module Process - RDoc Documentation

# module Process

The module contains several groups of functionality for handling OS processes:

- Low-level property introspection and management of the current process, like `Process.argv0`, `Process.pid`;

- Low-level introspection of other processes, like `Process.getpgid`, `Process.getpriority`;

- Management of the current process: `Process.abort`, `Process.exit`, `Process.daemon`, etc. (for convenience, most of those are also available as global functions and module functions of `Kernel`);

- Creation and management of child processes: `Process.fork`, `Process.spawn`, and related methods;

- Management of low-level system clock: `Process.times` and `Process.clock_gettime`, which could be important for proper benchmarking and other elapsed time measurement tasks.

### Constants

CLOCK_BOOTTIME

  see `Process.clock_gettime`

CLOCK_BOOTTIME_ALARM

  see `Process.clock_gettime`

CLOCK_MONOTONIC

  see `Process.clock_gettime`

CLOCK_MONOTONIC_COARSE

  see `Process.clock_gettime`

CLOCK_MONOTONIC_FAST

  see `Process.clock_gettime`

CLOCK_MONOTONIC_PRECISE

  see `Process.clock_gettime`

CLOCK_MONOTONIC_RAW

  see `Process.clock_gettime`

CLOCK_MONOTONIC_RAW_APPROX

  see `Process.clock_gettime`

CLOCK_PROCESS_CPUTIME_ID

  see `Process.clock_gettime`

CLOCK_PROF

  see `Process.clock_gettime`

CLOCK_REALTIME

  see `Process.clock_gettime`

CLOCK_REALTIME_ALARM

  see `Process.clock_gettime`

CLOCK_REALTIME_COARSE

  see `Process.clock_gettime`

CLOCK_REALTIME_FAST

  see `Process.clock_gettime`

CLOCK_REALTIME_PRECISE

  see `Process.clock_gettime`

CLOCK_SECOND

  see `Process.clock_gettime`

CLOCK_TAI

  see `Process.clock_gettime`

CLOCK_THREAD_CPUTIME_ID

  see `Process.clock_gettime`

CLOCK_UPTIME

  see `Process.clock_gettime`

CLOCK_UPTIME_FAST

  see `Process.clock_gettime`

CLOCK_UPTIME_PRECISE

  see `Process.clock_gettime`

CLOCK_UPTIME_RAW

  see `Process.clock_gettime`

CLOCK_UPTIME_RAW_APPROX

  see `Process.clock_gettime`

CLOCK_VIRTUAL

  see `Process.clock_gettime`

PRIO_PGRP

  see `Process.setpriority`

PRIO_PROCESS

  see `Process.setpriority`

PRIO_USER

  see `Process.setpriority`

RLIMIT_AS

  Maximum size of the process's virtual memory (address space) in bytes.

  see the system getrlimit(2) manual for details.

RLIMIT_CORE

  Maximum size of the core file.

  see the system getrlimit(2) manual for details.

RLIMIT_CPU

  CPU time limit in seconds.

  see the system getrlimit(2) manual for details.

RLIMIT_DATA

  Maximum size of the process's data segment.

  see the system getrlimit(2) manual for details.

RLIMIT_FSIZE

  Maximum size of files that the process may create.

  see the system getrlimit(2) manual for details.

RLIMIT_MEMLOCK

  Maximum number of bytes of memory that may be locked into RAM.

  see the system getrlimit(2) manual for details.

RLIMIT_MSGQUEUE

  Specifies the limit on the number of bytes that can be allocated for POSIX message queues for the real user ID of the calling process.

  see the system getrlimit(2) manual for details.

RLIMIT_NICE

  Specifies a ceiling to which the process's nice value can be raised.

  see the system getrlimit(2) manual for details.

RLIMIT_NOFILE

  Specifies a value one greater than the maximum file descriptor number that can be opened by this process.

  see the system getrlimit(2) manual for details.

RLIMIT_NPROC

  The maximum number of processes that can be created for the real user ID of the calling process.

  see the system getrlimit(2) manual for details.

RLIMIT_RSS

  Specifies the limit (in pages) of the process's resident set.

  see the system getrlimit(2) manual for details.

RLIMIT_RTPRIO

  Specifies a ceiling on the real-time priority that may be set for this process.

  see the system getrlimit(2) manual for details.

RLIMIT_RTTIME

  Specifies limit on CPU time this process scheduled under a real-time scheduling policy can consume.

  see the system getrlimit(2) manual for details.

RLIMIT_SBSIZE

  Maximum size of the socket buffer.

RLIMIT_SIGPENDING

  Specifies a limit on the number of signals that may be queued for the real user ID of the calling process.

  see the system getrlimit(2) manual for details.

RLIMIT_STACK

  Maximum size of the stack, in bytes.

  see the system getrlimit(2) manual for details.

RLIM_INFINITY

  see `Process.setrlimit`

RLIM_SAVED_CUR

  see `Process.setrlimit`

RLIM_SAVED_MAX

  see `Process.setrlimit`

WNOHANG

  see `Process.wait`

WUNTRACED

  see `Process.wait`

### Public Class Methods

abort click to toggle source
Kernel::abort([msg])
abort([msg])

Terminate execution immediately, effectively by calling `Kernel.exit(false)`. If msg is given, it is written to STDERR prior to terminating.

    static VALUE
    f_abort(int c, const VALUE *a, VALUE _)
    {
        rb_f_abort(c, a);
        UNREACHABLE_RETURN(Qnil);
    }

argv0 → frozen_string click to toggle source

Returns the name of the script being executed. The value is not affected by assigning a new value to $0.

This method first appeared in Ruby 2.1 to serve as a global variable free means to get the script name.

    static VALUE
    proc_argv0(VALUE process)
    {
        return rb_orig_progname;
    }

clock_getres(clock_id [, unit]) → number click to toggle source

Returns an estimate of the resolution of a `clock_id` using the POSIX `clock_getres()` function.

Note the reported resolution is often inaccurate on most platforms due to underlying bugs for this function and therefore the reported resolution often differs from the actual resolution of the clock in practice. Inaccurate reported resolutions have been observed for various clocks including `CLOCK_MONOTONIC` and `CLOCK_MONOTONIC_RAW` when using Linux, macOS, BSD or AIX platforms, when using ARM processors, or when using virtualization.

`clock_id` specifies a kind of clock. See the document of `Process.clock_gettime` for details. `clock_id` can be a symbol as for `Process.clock_gettime`.

If the given `clock_id` is not supported, Errno::EINVAL is raised.

`unit` specifies the type of the return value. `Process.clock_getres` accepts `unit` as `Process.clock_gettime`. The default value, `:float_second`, is also the same as `Process.clock_gettime`.

`Process.clock_getres` also accepts `:hertz` as `unit`. `:hertz` means the reciprocal of `:float_second`.

`:hertz` can be used to obtain the exact value of the clock ticks per second for the times() function and CLOCKS_PER_SEC for the clock() function.

`Process.clock_getres(:TIMES_BASED_CLOCK_PROCESS_CPUTIME_ID, :hertz)` returns the clock ticks per second.

`Process.clock_getres(:CLOCK_BASED_CLOCK_PROCESS_CPUTIME_ID, :hertz)` returns CLOCKS_PER_SEC.

    p Process.clock_getres(Process::CLOCK_MONOTONIC)
    #=> 1.0e-09

    static VALUE
    rb_clock_getres(int argc, VALUE *argv, VALUE _)
    {
        struct timetick tt;
        timetick_int_t numerators[2];
        timetick_int_t denominators[2];
        int num_numerators = 0;
        int num_denominators = 0;

        VALUE unit = (rb_check_arity(argc, 1, 2) == 2) ? argv[1] : Qnil;
        VALUE clk_id = argv[0];

        if (SYMBOL_P(clk_id)) {
    #ifdef RUBY_GETTIMEOFDAY_BASED_CLOCK_REALTIME
            if (clk_id == RUBY_GETTIMEOFDAY_BASED_CLOCK_REALTIME) {
                tt.giga_count = 0;
                tt.count = 1000;
                denominators[num_denominators++] = 1000000000;
                goto success;
            }
    #endif

    #ifdef RUBY_TIME_BASED_CLOCK_REALTIME
            if (clk_id == RUBY_TIME_BASED_CLOCK_REALTIME) {
                tt.giga_count = 1;
                tt.count = 0;
                denominators[num_denominators++] = 1000000000;
                goto success;
            }
    #endif

    #ifdef RUBY_TIMES_BASED_CLOCK_MONOTONIC
            if (clk_id == RUBY_TIMES_BASED_CLOCK_MONOTONIC) {
                tt.count = 1;
                tt.giga_count = 0;
                denominators[num_denominators++] = get_clk_tck();
                goto success;
            }
    #endif

    #ifdef RUBY_GETRUSAGE_BASED_CLOCK_PROCESS_CPUTIME_ID
            if (clk_id == RUBY_GETRUSAGE_BASED_CLOCK_PROCESS_CPUTIME_ID) {
                tt.giga_count = 0;
                tt.count = 1000;
                denominators[num_denominators++] = 1000000000;
                goto success;
            }
    #endif

    #ifdef RUBY_TIMES_BASED_CLOCK_PROCESS_CPUTIME_ID
            if (clk_id == RUBY_TIMES_BASED_CLOCK_PROCESS_CPUTIME_ID) {
                tt.count = 1;
                tt.giga_count = 0;
                denominators[num_denominators++] = get_clk_tck();
                goto success;
            }
    #endif

    #ifdef RUBY_CLOCK_BASED_CLOCK_PROCESS_CPUTIME_ID
            if (clk_id == RUBY_CLOCK_BASED_CLOCK_PROCESS_CPUTIME_ID) {
                tt.count = 1;
                tt.giga_count = 0;
                denominators[num_denominators++] = CLOCKS_PER_SEC;
                goto success;
            }
    #endif

    #ifdef RUBY_MACH_ABSOLUTE_TIME_BASED_CLOCK_MONOTONIC
            if (clk_id == RUBY_MACH_ABSOLUTE_TIME_BASED_CLOCK_MONOTONIC) {
                const mach_timebase_info_data_t *info = get_mach_timebase_info();
                tt.count = 1;
                tt.giga_count = 0;
                numerators[num_numerators++] = info->numer;
                denominators[num_denominators++] = info->denom;
                denominators[num_denominators++] = 1000000000;
                goto success;
            }
    #endif
        }
        else {
    #if defined(HAVE_CLOCK_GETRES)
            struct timespec ts;
            clockid_t c = NUM2CLOCKID(clk_id);
            int ret = clock_getres(c, &ts);
            if (ret == -1)
                rb_sys_fail("clock_getres");
            tt.count = (int32_t)ts.tv_nsec;
            tt.giga_count = ts.tv_sec;
            denominators[num_denominators++] = 1000000000;
            goto success;
    #endif
        }
        /* EINVAL emulates clock_getres behavior when clock_id is invalid. */
        rb_syserr_fail(EINVAL, 0);

      success:
        if (unit == ID2SYM(id_hertz)) {
            return timetick2dblnum_reciprocal(&tt, numerators, num_numerators, denominators, num_denominators);
        }
        else {
            return make_clock_result(&tt, numerators, num_numerators, denominators, num_denominators, unit);
        }
    }

clock_gettime(clock_id [, unit]) → number click to toggle source

Returns a time returned by POSIX `clock_gettime`() function.

    p Process.clock_gettime(Process::CLOCK_MONOTONIC)
    #=> 896053.968060096

`clock_id` specifies a kind of clock. It is specified as a constant which begins with `Process::CLOCK_` such as `Process::CLOCK_REALTIME` and `Process::CLOCK_MONOTONIC`.

The supported constants depends on OS and version. Ruby provides following types of `clock_id` if available.

`CLOCK_REALTIME`

  SUSv2 to 4, Linux 2.5.63, FreeBSD 3.0, NetBSD 2.0, OpenBSD 2.1, macOS 10.12

`CLOCK_MONOTONIC`

  SUSv3 to 4, Linux 2.5.63, FreeBSD 3.0, NetBSD 2.0, OpenBSD 3.4, macOS 10.12

`CLOCK_PROCESS_CPUTIME_ID`

  SUSv3 to 4, Linux 2.5.63, FreeBSD 9.3, OpenBSD 5.4, macOS 10.12

`CLOCK_THREAD_CPUTIME_ID`

  SUSv3 to 4, Linux 2.5.63, FreeBSD 7.1, OpenBSD 5.4, macOS 10.12

`CLOCK_VIRTUAL`

  FreeBSD 3.0, OpenBSD 2.1

`CLOCK_PROF`

  FreeBSD 3.0, OpenBSD 2.1

`CLOCK_REALTIME_FAST`

  FreeBSD 8.1

`CLOCK_REALTIME_PRECISE`

  FreeBSD 8.1

`CLOCK_REALTIME_COARSE`

  Linux 2.6.32

`CLOCK_REALTIME_ALARM`

  Linux 3.0

`CLOCK_MONOTONIC_FAST`

  FreeBSD 8.1

`CLOCK_MONOTONIC_PRECISE`

  FreeBSD 8.1

`CLOCK_MONOTONIC_COARSE`

  Linux 2.6.32

`CLOCK_MONOTONIC_RAW`

  Linux 2.6.28, macOS 10.12

`CLOCK_MONOTONIC_RAW_APPROX`

  macOS 10.12

`CLOCK_BOOTTIME`

  Linux 2.6.39

`CLOCK_BOOTTIME_ALARM`

  Linux 3.0

`CLOCK_UPTIME`

  FreeBSD 7.0, OpenBSD 5.5

`CLOCK_UPTIME_FAST`

  FreeBSD 8.1

`CLOCK_UPTIME_RAW`

  macOS 10.12

`CLOCK_UPTIME_RAW_APPROX`

  macOS 10.12

`CLOCK_UPTIME_PRECISE`

  FreeBSD 8.1

`CLOCK_SECOND`

  FreeBSD 8.1

`CLOCK_TAI`

  Linux 3.10

Note that SUS stands for Single Unix Specification. SUS contains POSIX and `clock_gettime` is defined in the POSIX part. SUS defines `CLOCK_REALTIME` mandatory but `CLOCK_MONOTONIC`, `CLOCK_PROCESS_CPUTIME_ID` and `CLOCK_THREAD_CPUTIME_ID` are optional.

Also, several symbols are accepted as `clock_id`. There are emulations for `clock_gettime`().

For example, `Process::CLOCK_REALTIME` is defined as `:GETTIMEOFDAY_BASED_CLOCK_REALTIME` when `clock_gettime`() is not available.

Emulations for `CLOCK_REALTIME`:

:GETTIMEOFDAY_BASED_CLOCK_REALTIME

  Use gettimeofday() defined by SUS. (SUSv4 obsoleted it, though.) The resolution is 1 microsecond.

:TIME_BASED_CLOCK_REALTIME

  Use time() defined by ISO C. The resolution is 1 second.

Emulations for `CLOCK_MONOTONIC`:

:MACH_ABSOLUTE_TIME_BASED_CLOCK_MONOTONIC

  Use mach_absolute_time(), available on Darwin. The resolution is CPU dependent.

:TIMES_BASED_CLOCK_MONOTONIC

  Use the result value of times() defined by POSIX. POSIX defines it as “times() shall return the elapsed real time, in clock ticks, since an arbitrary point in the past (for example, system start-up time)”. For example, GNU/Linux returns a value based on jiffies and it is monotonic. However, 4.4BSD uses gettimeofday() and it is not monotonic. (FreeBSD uses `clock_gettime`(`CLOCK_MONOTONIC`) instead, though.) The resolution is the clock tick. “getconf CLK_TCK” command shows the clock ticks per second. (The clock ticks per second is defined by HZ macro in older systems.) If it is 100 and clock_t is 32 bits integer type, the resolution is 10 millisecond and cannot represent over 497 days.

Emulations for `CLOCK_PROCESS_CPUTIME_ID`:

:GETRUSAGE_BASED_CLOCK_PROCESS_CPUTIME_ID

  Use getrusage() defined by SUS. getrusage() is used with RUSAGE_SELF to obtain the time only for the calling process (excluding the time for child processes). The result is addition of user time (ru_utime) and system time (ru_stime). The resolution is 1 microsecond.

:TIMES_BASED_CLOCK_PROCESS_CPUTIME_ID

  Use times() defined by POSIX. The result is addition of user time (tms_utime) and system time (tms_stime). tms_cutime and tms_cstime are ignored to exclude the time for child processes. The resolution is the clock tick. “getconf CLK_TCK” command shows the clock ticks per second. (The clock ticks per second is defined by HZ macro in older systems.) If it is 100, the resolution is 10 millisecond.

:CLOCK_BASED_CLOCK_PROCESS_CPUTIME_ID

  Use clock() defined by ISO C. The resolution is 1/CLOCKS_PER_SEC. CLOCKS_PER_SEC is the C-level macro defined by time.h. SUS defines CLOCKS_PER_SEC is 1000000. Non-Unix systems may define it a different value, though. If CLOCKS_PER_SEC is 1000000 as SUS, the resolution is 1 microsecond. If CLOCKS_PER_SEC is 1000000 and clock_t is 32 bits integer type, it cannot represent over 72 minutes.

If the given `clock_id` is not supported, Errno::EINVAL is raised.

`unit` specifies a type of the return value.

:float_second

  number of seconds as a float (default)

:float_millisecond

  number of milliseconds as a float

:float_microsecond

  number of microseconds as a float

:second

  number of seconds as an integer

:millisecond

  number of milliseconds as an integer

:microsecond

  number of microseconds as an integer

:nanosecond

  number of nanoseconds as an integer

The underlying function, `clock_gettime`(), returns a number of nanoseconds. `Float` object (IEEE 754 double) is not enough to represent the return value for `CLOCK_REALTIME`. If the exact nanoseconds value is required, use `:nanoseconds` as the `unit`.

The origin (zero) of the returned value varies. For example, system start up time, process start up time, the Epoch, etc.

The origin in `CLOCK_REALTIME` is defined as the Epoch (1970-01-01 00:00:00 UTC). But some systems count leap seconds and others doesn't. So the result can be interpreted differently across systems. `Time.now` is recommended over `CLOCK_REALTIME`.

    static VALUE
    rb_clock_gettime(int argc, VALUE *argv, VALUE _)
    {
        int ret;

        struct timetick tt;
        timetick_int_t numerators[2];
        timetick_int_t denominators[2];
        int num_numerators = 0;
        int num_denominators = 0;

        VALUE unit = (rb_check_arity(argc, 1, 2) == 2) ? argv[1] : Qnil;
        VALUE clk_id = argv[0];

        if (SYMBOL_P(clk_id)) {
            /*
             * Non-clock_gettime clocks are provided by symbol clk_id.
             */
    #ifdef HAVE_GETTIMEOFDAY
            /*
             * GETTIMEOFDAY_BASED_CLOCK_REALTIME is used for
             * CLOCK_REALTIME if clock_gettime is not available.
             */
    #define RUBY_GETTIMEOFDAY_BASED_CLOCK_REALTIME ID2SYM(id_GETTIMEOFDAY_BASED_CLOCK_REALTIME)
            if (clk_id == RUBY_GETTIMEOFDAY_BASED_CLOCK_REALTIME) {
                struct timeval tv;
                ret = gettimeofday(&tv, 0);
                if (ret != 0)
                    rb_sys_fail("gettimeofday");
                tt.giga_count = tv.tv_sec;
                tt.count = (int32_t)tv.tv_usec * 1000;
                denominators[num_denominators++] = 1000000000;
                goto success;
            }
    #endif

    #define RUBY_TIME_BASED_CLOCK_REALTIME ID2SYM(id_TIME_BASED_CLOCK_REALTIME)
            if (clk_id == RUBY_TIME_BASED_CLOCK_REALTIME) {
                time_t t;
                t = time(NULL);
                if (t == (time_t)-1)
                    rb_sys_fail("time");
                tt.giga_count = t;
                tt.count = 0;
                denominators[num_denominators++] = 1000000000;
                goto success;
            }

    #ifdef HAVE_TIMES
    #define RUBY_TIMES_BASED_CLOCK_MONOTONIC \
            ID2SYM(id_TIMES_BASED_CLOCK_MONOTONIC)
            if (clk_id == RUBY_TIMES_BASED_CLOCK_MONOTONIC) {
                struct tms buf;
                clock_t c;
                unsigned_clock_t uc;
                c = times(&buf);
                if (c ==  (clock_t)-1)
                    rb_sys_fail("times");
                uc = (unsigned_clock_t)c;
                tt.count = (int32_t)(uc % 1000000000);
                tt.giga_count = (uc / 1000000000);
                denominators[num_denominators++] = get_clk_tck();
                goto success;
            }
    #endif

    #ifdef RUSAGE_SELF
    #define RUBY_GETRUSAGE_BASED_CLOCK_PROCESS_CPUTIME_ID \
            ID2SYM(id_GETRUSAGE_BASED_CLOCK_PROCESS_CPUTIME_ID)
            if (clk_id == RUBY_GETRUSAGE_BASED_CLOCK_PROCESS_CPUTIME_ID) {
                struct rusage usage;
                int32_t usec;
                ret = getrusage(RUSAGE_SELF, &usage);
                if (ret != 0)
                    rb_sys_fail("getrusage");
                tt.giga_count = usage.ru_utime.tv_sec + usage.ru_stime.tv_sec;
                usec = (int32_t)(usage.ru_utime.tv_usec + usage.ru_stime.tv_usec);
                if (1000000 <= usec) {
                    tt.giga_count++;
                    usec -= 1000000;
                }
                tt.count = usec * 1000;
                denominators[num_denominators++] = 1000000000;
                goto success;
            }
    #endif

    #ifdef HAVE_TIMES
    #define RUBY_TIMES_BASED_CLOCK_PROCESS_CPUTIME_ID \
            ID2SYM(id_TIMES_BASED_CLOCK_PROCESS_CPUTIME_ID)
            if (clk_id == RUBY_TIMES_BASED_CLOCK_PROCESS_CPUTIME_ID) {
                struct tms buf;
                unsigned_clock_t utime, stime;
                if (times(&buf) ==  (clock_t)-1)
                    rb_sys_fail("times");
                utime = (unsigned_clock_t)buf.tms_utime;
                stime = (unsigned_clock_t)buf.tms_stime;
                tt.count = (int32_t)((utime % 1000000000) + (stime % 1000000000));
                tt.giga_count = (utime / 1000000000) + (stime / 1000000000);
                if (1000000000 <= tt.count) {
                    tt.count -= 1000000000;
                    tt.giga_count++;
                }
                denominators[num_denominators++] = get_clk_tck();
                goto success;
            }
    #endif

    #define RUBY_CLOCK_BASED_CLOCK_PROCESS_CPUTIME_ID \
            ID2SYM(id_CLOCK_BASED_CLOCK_PROCESS_CPUTIME_ID)
            if (clk_id == RUBY_CLOCK_BASED_CLOCK_PROCESS_CPUTIME_ID) {
                clock_t c;
                unsigned_clock_t uc;
                errno = 0;
                c = clock();
                if (c == (clock_t)-1)
                    rb_sys_fail("clock");
                uc = (unsigned_clock_t)c;
                tt.count = (int32_t)(uc % 1000000000);
                tt.giga_count = uc / 1000000000;
                denominators[num_denominators++] = CLOCKS_PER_SEC;
                goto success;
            }

    #ifdef __APPLE__
    #define RUBY_MACH_ABSOLUTE_TIME_BASED_CLOCK_MONOTONIC ID2SYM(id_MACH_ABSOLUTE_TIME_BASED_CLOCK_MONOTONIC)
            if (clk_id == RUBY_MACH_ABSOLUTE_TIME_BASED_CLOCK_MONOTONIC) {
                const mach_timebase_info_data_t *info = get_mach_timebase_info();
                uint64_t t = mach_absolute_time();
                tt.count = (int32_t)(t % 1000000000);
                tt.giga_count = t / 1000000000;
                numerators[num_numerators++] = info->numer;
                denominators[num_denominators++] = info->denom;
                denominators[num_denominators++] = 1000000000;
                goto success;
            }
    #endif
        }
        else {
    #if defined(HAVE_CLOCK_GETTIME)
            struct timespec ts;
            clockid_t c;
            c = NUM2CLOCKID(clk_id);
            ret = clock_gettime(c, &ts);
            if (ret == -1)
                rb_sys_fail("clock_gettime");
            tt.count = (int32_t)ts.tv_nsec;
            tt.giga_count = ts.tv_sec;
            denominators[num_denominators++] = 1000000000;
            goto success;
    #endif
        }
        /* EINVAL emulates clock_gettime behavior when clock_id is invalid. */
        rb_syserr_fail(EINVAL, 0);

      success:
        return make_clock_result(&tt, numerators, num_numerators, denominators, num_denominators, unit);
    }

daemon() → 0 click to toggle source
daemon(nochdir=nil,noclose=nil) → 0

Detach the process from controlling terminal and run in the background as system daemon. Unless the argument nochdir is true (i.e. non false), it changes the current working directory to the root (“/”). Unless the argument noclose is true, daemon() will redirect standard input, standard output and standard error to /dev/null. Return zero on success, or raise one of Errno::*.

    static VALUE
    proc_daemon(int argc, VALUE *argv, VALUE _)
    {
        int n, nochdir = FALSE, noclose = FALSE;

        switch (rb_check_arity(argc, 0, 2)) {
          case 2: noclose = TO_BOOL(argv[1], "noclose");
          case 1: nochdir = TO_BOOL(argv[0], "nochdir");
        }

        prefork();
        n = rb_daemon(nochdir, noclose);
        if (n < 0) rb_sys_fail("daemon");
        return INT2FIX(n);
    }

detach(pid) → thread click to toggle source

Some operating systems retain the status of terminated child processes until the parent collects that status (normally using some variant of `wait()`). If the parent never collects this status, the child stays around as a zombie process. `Process::detach` prevents this by setting up a separate Ruby thread whose sole job is to reap the status of the process pid when it terminates. Use detach only when you do not intend to explicitly wait for the child to terminate.

The waiting thread returns the exit status of the detached process when it terminates, so you can use `Thread#join` to know the result. If specified pid is not a valid child process ID, the thread returns `nil` immediately.

The waiting thread has pid method which returns the pid.

In this first example, we don't reap the first child process, so it appears as a zombie in the process status display.

    p1 = fork { sleep 0.1 }
    p2 = fork { sleep 0.2 }
    Process.waitpid(p2)
    sleep 2
    system("ps -ho pid,state -p #{p1}")

produces:

    27389 Z

In the next example, `Process::detach` is used to reap the child automatically.

    p1 = fork { sleep 0.1 }
    p2 = fork { sleep 0.2 }
    Process.detach(p1)
    Process.waitpid(p2)
    sleep 2
    system("ps -ho pid,state -p #{p1}")

(produces no output)

    static VALUE
    proc_detach(VALUE obj, VALUE pid)
    {
        return rb_detach_process(NUM2PIDT(pid));
    }

egid → integer click to toggle source
Process::GID.eid → integer
Process::Sys.geteid → integer

Returns the effective group ID for this process. Not available on all platforms.

    Process.egid   #=> 500

    static VALUE
    proc_getegid(VALUE obj)
    {
        rb_gid_t egid = getegid();

        return GIDT2NUM(egid);
    }

egid = integer → integer click to toggle source

Sets the effective group ID for this process. Not available on all platforms.

    static VALUE
    proc_setegid(VALUE obj, VALUE egid)
    {
    #if defined(HAVE_SETRESGID) || defined(HAVE_SETREGID) || defined(HAVE_SETEGID) || defined(HAVE_SETGID)
        rb_gid_t gid;
    #endif

        check_gid_switch();

    #if defined(HAVE_SETRESGID) || defined(HAVE_SETREGID) || defined(HAVE_SETEGID) || defined(HAVE_SETGID)
        gid = OBJ2GID(egid);
    #endif

    #if defined(HAVE_SETRESGID)
        if (setresgid(-1, gid, -1) < 0) rb_sys_fail(0);
    #elif defined HAVE_SETREGID
        if (setregid(-1, gid) < 0) rb_sys_fail(0);
    #elif defined HAVE_SETEGID
        if (setegid(gid) < 0) rb_sys_fail(0);
    #elif defined HAVE_SETGID
        if (gid == getgid()) {
            if (setgid(gid) < 0) rb_sys_fail(0);
        }
        else {
            rb_notimplement();
        }
    #else
        rb_notimplement();
    #endif
        return egid;
    }

euid → integer click to toggle source
Process::UID.eid → integer
Process::Sys.geteuid → integer

Returns the effective user ID for this process.

    Process.euid   #=> 501

    static VALUE
    proc_geteuid(VALUE obj)
    {
        rb_uid_t euid = geteuid();
        return UIDT2NUM(euid);
    }

euid= user click to toggle source

Sets the effective user ID for this process. Not available on all platforms.

    static VALUE
    proc_seteuid_m(VALUE mod, VALUE euid)
    {
        check_uid_switch();
        proc_seteuid(OBJ2UID(euid));
        return euid;
    }

exec([env,] command... [,options]) click to toggle source

Replaces the current process by running the given external command, which can take one of the following forms:

`exec(commandline)`

  command line string which is passed to the standard shell

`exec(cmdname, arg1, ...)`

  command name and one or more arguments (no shell)

`exec([cmdname, argv0], arg1, ...)`

  command name, argv and zero or more arguments (no shell)

In the first form, the string is taken as a command line that is subject to shell expansion before being executed.

The standard shell always means `"/bin/sh"` on Unix-like systems, same as `ENV["RUBYSHELL"]` (or `ENV["COMSPEC"]` on Windows NT series), and similar.

If the string from the first form (`exec("command")`) follows these simple rules:

- no meta characters

- no shell reserved word and no special built-in

- Ruby invokes the command directly without shell

You can force shell invocation by adding “;” to the string (because “;” is a meta character).

Note that this behavior is observable by pid obtained (return value of spawn() and `IO#pid` for `IO.popen`) is the pid of the invoked command, not shell.

In the second form (`exec("command1", "arg1", ...)`), the first is taken as a command name and the rest are passed as parameters to command with no shell expansion.

In the third form (`exec(["command", "argv0"], "arg1", ...)`), starting a two-element array at the beginning of the command, the first element is the command to be executed, and the second argument is used as the `argv[0]` value, which may show up in process listings.

In order to execute the command, one of the `exec(2)` system calls are used, so the running command may inherit some of the environment of the original program (including open file descriptors).

This behavior is modified by the given `env` and `options` parameters. See `::spawn` for details.

If the command fails to execute (typically Errno::ENOENT when it was not found) a `SystemCallError` exception is raised.

This method modifies process attributes according to given `options` before `exec(2)` system call. See `::spawn` for more details about the given `options`.

The modified attributes may be retained when `exec(2)` system call fails.

For example, hard resource limits are not restorable.

Consider to create a child process using `::spawn` or `Kernel#system` if this is not acceptable.

    exec "echo *"       # echoes list of files in current directory
    # never get here

    exec "echo", "*"    # echoes an asterisk
    # never get here

    static VALUE
    f_exec(int c, const VALUE *a, VALUE _)
    {
        rb_f_exec(c, a);
        UNREACHABLE_RETURN(Qnil);
    }

exit(status=true) click to toggle source
Kernel::exit(status=true)
Process::exit(status=true)

Initiates the termination of the Ruby script by raising the `SystemExit` exception. This exception may be caught. The optional parameter is used to return a status code to the invoking environment. `true` and `FALSE` of status means success and failure respectively. The interpretation of other integer values are system dependent.

    begin
      exit
      puts "never get here"
    rescue SystemExit
      puts "rescued a SystemExit exception"
    end
    puts "after begin block"

produces:

    rescued a SystemExit exception
    after begin block

Just prior to termination, Ruby executes any `at_exit` functions (see Kernel::at_exit) and runs any object finalizers (see `ObjectSpace::define_finalizer`).

    at_exit { puts "at_exit function" }
    ObjectSpace.define_finalizer("string",  proc { puts "in finalizer" })
    exit

produces:

    at_exit function
    in finalizer

    static VALUE
    f_exit(int c, const VALUE *a, VALUE _)
    {
        rb_f_exit(c, a);
        UNREACHABLE_RETURN(Qnil);
    }

exit!(status=false) click to toggle source

Exits the process immediately. No exit handlers are run. status is returned to the underlying system as the exit status.

    Process.exit!(true)

    static VALUE
    rb_f_exit_bang(int argc, VALUE *argv, VALUE obj)
    {
        int istatus;

        if (rb_check_arity(argc, 0, 1) == 1) {
            istatus = exit_status_code(argv[0]);
        }
        else {
            istatus = EXIT_FAILURE;
        }
        _exit(istatus);

        UNREACHABLE_RETURN(Qnil);
    }

fork [{ block }] → integer or nil click to toggle source
fork [{ block }] → integer or nil

Creates a subprocess. If a block is specified, that block is run in the subprocess, and the subprocess terminates with a status of zero. Otherwise, the `fork` call returns twice, once in the parent, returning the process ID of the child, and once in the child, returning nil. The child process can exit using `Kernel.exit!` to avoid running any `at_exit` functions. The parent process should use `Process.wait` to collect the termination statuses of its children or use `Process.detach` to register disinterest in their status; otherwise, the operating system may accumulate zombie processes.

The thread calling fork is the only thread in the created child process. fork doesn't copy other threads.

If fork is not usable, Process.respond_to?(:fork) returns false.

Note that fork(2) is not available on some platforms like Windows and NetBSD 4. Therefore you should use spawn() instead of fork().

    static VALUE
    rb_f_fork(VALUE obj)
    {
        rb_pid_t pid;

        switch (pid = rb_fork_ruby(NULL)) {
          case 0:
            rb_thread_atfork();
            if (rb_block_given_p()) {
                int status;
                rb_protect(rb_yield, Qundef, &status);
                ruby_stop(status);
            }
            return Qnil;

          case -1:
            rb_sys_fail("fork(2)");
            return Qnil;

          default:
            return PIDT2NUM(pid);
        }
    }

getpgid(pid) → integer click to toggle source

Returns the process group ID for the given process id. Not available on all platforms.

    Process.getpgid(Process.ppid())   #=> 25527

    static VALUE
    proc_getpgid(VALUE obj, VALUE pid)
    {
        rb_pid_t i;

        i = getpgid(NUM2PIDT(pid));
        if (i < 0) rb_sys_fail(0);
        return PIDT2NUM(i);
    }

getpgrp → integer click to toggle source

Returns the process group ID for this process. Not available on all platforms.

    Process.getpgid(0)   #=> 25527
    Process.getpgrp      #=> 25527

    static VALUE
    proc_getpgrp(VALUE _)
    {
        rb_pid_t pgrp;

    #if defined(HAVE_GETPGRP) && defined(GETPGRP_VOID)
        pgrp = getpgrp();
        if (pgrp < 0) rb_sys_fail(0);
        return PIDT2NUM(pgrp);
    #else /* defined(HAVE_GETPGID) */
        pgrp = getpgid(0);
        if (pgrp < 0) rb_sys_fail(0);
        return PIDT2NUM(pgrp);
    #endif
    }

getpriority(kind, integer) → integer click to toggle source

Gets the scheduling priority for specified process, process group, or user. kind indicates the kind of entity to find: one of `Process::PRIO_PGRP`, `Process::PRIO_USER`, or `Process::PRIO_PROCESS`. integer is an id indicating the particular process, process group, or user (an id of 0 means current). Lower priorities are more favorable for scheduling. Not available on all platforms.

    Process.getpriority(Process::PRIO_USER, 0)      #=> 19
    Process.getpriority(Process::PRIO_PROCESS, 0)   #=> 19

    static VALUE
    proc_getpriority(VALUE obj, VALUE which, VALUE who)
    {
        int prio, iwhich, iwho;

        iwhich = NUM2INT(which);
        iwho   = NUM2INT(who);

        errno = 0;
        prio = getpriority(iwhich, iwho);
        if (errno) rb_sys_fail(0);
        return INT2FIX(prio);
    }

getrlimit(resource) → [cur_limit, max_limit] click to toggle source

Gets the resource limit of the process. cur_limit means current (soft) limit and max_limit means maximum (hard) limit.

resource indicates the kind of resource to limit. It is specified as a symbol such as `:CORE`, a string such as `"CORE"` or a constant such as `Process::RLIMIT_CORE`. See `Process.setrlimit` for details.

cur_limit and max_limit may be `Process::RLIM_INFINITY`, `Process::RLIM_SAVED_MAX` or `Process::RLIM_SAVED_CUR`. See `Process.setrlimit` and the system getrlimit(2) manual for details.

    static VALUE
    proc_getrlimit(VALUE obj, VALUE resource)
    {
        struct rlimit rlim;

        if (getrlimit(rlimit_resource_type(resource), &rlim) < 0) {
            rb_sys_fail("getrlimit");
        }
        return rb_assoc_new(RLIM2NUM(rlim.rlim_cur), RLIM2NUM(rlim.rlim_max));
    }

getsid() → integer click to toggle source
getsid(pid) → integer

Returns the session ID for the given process id. If not given, return current process sid. Not available on all platforms.

    Process.getsid()                #=> 27422
    Process.getsid(0)               #=> 27422
    Process.getsid(Process.pid())   #=> 27422

    static VALUE
    proc_getsid(int argc, VALUE *argv, VALUE _)
    {
        rb_pid_t sid;
        rb_pid_t pid = 0;

        if (rb_check_arity(argc, 0, 1) == 1 && !NIL_P(argv[0]))
            pid = NUM2PIDT(argv[0]);

        sid = getsid(pid);
        if (sid < 0) rb_sys_fail(0);
        return PIDT2NUM(sid);
    }

gid → integer click to toggle source
Process::GID.rid → integer
Process::Sys.getgid → integer

Returns the (real) group ID for this process.

    Process.gid   #=> 500

    static VALUE
    proc_getgid(VALUE obj)
    {
        rb_gid_t gid = getgid();
        return GIDT2NUM(gid);
    }

gid= integer → integer click to toggle source

Sets the group ID for this process.

    static VALUE
    proc_setgid(VALUE obj, VALUE id)
    {
        rb_gid_t gid;

        check_gid_switch();

        gid = OBJ2GID(id);
    #if defined(HAVE_SETRESGID)
        if (setresgid(gid, -1, -1) < 0) rb_sys_fail(0);
    #elif defined HAVE_SETREGID
        if (setregid(gid, -1) < 0) rb_sys_fail(0);
    #elif defined HAVE_SETRGID
        if (setrgid(gid) < 0) rb_sys_fail(0);
    #elif defined HAVE_SETGID
        {
            if (getegid() == gid) {
                if (setgid(gid) < 0) rb_sys_fail(0);
            }
            else {
                rb_notimplement();
            }
        }
    #endif
        return GIDT2NUM(gid);
    }

groups → array click to toggle source

Get an `Array` of the group IDs in the supplemental group access list for this process.

    Process.groups   #=> [27, 6, 10, 11]

Note that this method is just a wrapper of getgroups(2). This means that the following characteristics of the result completely depend on your system:

- the result is sorted

- the result includes effective GIDs

- the result does not include duplicated GIDs

You can make sure to get a sorted unique `GID` list of the current process by this expression:

    Process.groups.uniq.sort

    static VALUE
    proc_getgroups(VALUE obj)
    {
        VALUE ary, tmp;
        int i, ngroups;
        rb_gid_t *groups;

        ngroups = getgroups(0, NULL);
        if (ngroups == -1)
            rb_sys_fail(0);

        groups = ALLOCV_N(rb_gid_t, tmp, ngroups);

        ngroups = getgroups(ngroups, groups);
        if (ngroups == -1)
            rb_sys_fail(0);

        ary = rb_ary_new();
        for (i = 0; i < ngroups; i++)
            rb_ary_push(ary, GIDT2NUM(groups[i]));

        ALLOCV_END(tmp);

        return ary;
    }

groups= array → array click to toggle source

`Set` the supplemental group access list to the given `Array` of group IDs.

    Process.groups   #=> [0, 1, 2, 3, 4, 6, 10, 11, 20, 26, 27]
    Process.groups = [27, 6, 10, 11]   #=> [27, 6, 10, 11]
    Process.groups   #=> [27, 6, 10, 11]

    static VALUE
    proc_setgroups(VALUE obj, VALUE ary)
    {
        int ngroups, i;
        rb_gid_t *groups;
        VALUE tmp;
        PREPARE_GETGRNAM;

        Check_Type(ary, T_ARRAY);

        ngroups = RARRAY_LENINT(ary);
        if (ngroups > maxgroups())
            rb_raise(rb_eArgError, "too many groups, %d max", maxgroups());

        groups = ALLOCV_N(rb_gid_t, tmp, ngroups);

        for (i = 0; i < ngroups; i++) {
            VALUE g = RARRAY_AREF(ary, i);

            groups[i] = OBJ2GID1(g);
        }
        FINISH_GETGRNAM;

        if (setgroups(ngroups, groups) == -1) /* ngroups <= maxgroups */
            rb_sys_fail(0);

        ALLOCV_END(tmp);

        return proc_getgroups(obj);
    }

initgroups(username, gid) → array click to toggle source

Initializes the supplemental group access list by reading the system group database and using all groups of which the given user is a member. The group with the specified gid is also added to the list. Returns the resulting `Array` of the gids of all the groups in the supplementary group access list. Not available on all platforms.

    Process.groups   #=> [0, 1, 2, 3, 4, 6, 10, 11, 20, 26, 27]
    Process.initgroups( "mgranger", 30 )   #=> [30, 6, 10, 11]
    Process.groups   #=> [30, 6, 10, 11]

    static VALUE
    proc_initgroups(VALUE obj, VALUE uname, VALUE base_grp)
    {
        if (initgroups(StringValueCStr(uname), OBJ2GID(base_grp)) != 0) {
            rb_sys_fail(0);
        }
        return proc_getgroups(obj);
    }

kill(signal, pid, ...) → integer click to toggle source

Sends the given signal to the specified process id(s) if pid is positive. If pid is zero, signal is sent to all processes whose group ID is equal to the group ID of the process. If pid is negative, results are dependent on the operating system. signal may be an integer signal number or a POSIX signal name (either with or without a `SIG` prefix). If signal is negative (or starts with a minus sign), kills process groups instead of processes. Not all signals are available on all platforms. The keys and values of `Signal.list` are known signal names and numbers, respectively.

    pid = fork do
       Signal.trap("HUP") { puts "Ouch!"; exit }
       # ... do some work ...
    end
    # ...
    Process.kill("HUP", pid)
    Process.wait

produces:

    Ouch!

If signal is an integer but wrong for signal, Errno::EINVAL or `RangeError` will be raised. Otherwise unless signal is a `String` or a `Symbol`, and a known signal name, `ArgumentError` will be raised.

Also, Errno::ESRCH or `RangeError` for invalid pid, Errno::EPERM when failed because of no privilege, will be raised. In these cases, signals may have been sent to preceding processes.

    static VALUE
    proc_rb_f_kill(int c, const VALUE *v, VALUE _)
    {
        return rb_f_kill(c, v);
    }

last_status → Process::Status or nil click to toggle source

Returns the status of the last executed child process in the current thread.

    Process.wait Process.spawn("ruby", "-e", "exit 13")
    Process.last_status   #=> #<Process::Status: pid 4825 exit 13>

If no child process has ever been executed in the current thread, this returns `nil`.

    Process.last_status   #=> nil

    static VALUE
    proc_s_last_status(VALUE mod)
    {
        return rb_last_status_get();
    }

maxgroups → integer click to toggle source

Returns the maximum number of gids allowed in the supplemental group access list.

    Process.maxgroups   #=> 32

    static VALUE
    proc_getmaxgroups(VALUE obj)
    {
        return INT2FIX(maxgroups());
    }

maxgroups= integer → integer click to toggle source

Sets the maximum number of gids allowed in the supplemental group access list.

    static VALUE
    proc_setmaxgroups(VALUE obj, VALUE val)
    {
        int ngroups = FIX2INT(val);
        int ngroups_max = get_sc_ngroups_max();

        if (ngroups <= 0)
            rb_raise(rb_eArgError, "maxgroups %d should be positive", ngroups);

        if (ngroups > RB_MAX_GROUPS)
            ngroups = RB_MAX_GROUPS;

        if (ngroups_max > 0 && ngroups > ngroups_max)
            ngroups = ngroups_max;

        _maxgroups = ngroups;

        return INT2FIX(_maxgroups);
    }

pid → integer click to toggle source

Returns the process id of this process. Not available on all platforms.

    Process.pid   #=> 27415

    static VALUE
    proc_get_pid(VALUE _)
    {
        return get_pid();
    }

ppid → integer click to toggle source

Returns the process id of the parent of this process. Returns untrustworthy value on Win32/64. Not available on all platforms.

    puts "I am #{Process.pid}"
    Process.fork { puts "Dad is #{Process.ppid}" }

produces:

    I am 27417
    Dad is 27417

    static VALUE
    proc_get_ppid(VALUE _)
    {
        return get_ppid();
    }

setpgid(pid, integer) → 0 click to toggle source

Sets the process group ID of pid (0 indicates this process) to integer. Not available on all platforms.

    static VALUE
    proc_setpgid(VALUE obj, VALUE pid, VALUE pgrp)
    {
        rb_pid_t ipid, ipgrp;

        ipid = NUM2PIDT(pid);
        ipgrp = NUM2PIDT(pgrp);

        if (setpgid(ipid, ipgrp) < 0) rb_sys_fail(0);
        return INT2FIX(0);
    }

setpgrp → 0 click to toggle source

Equivalent to `setpgid(0,0)`. Not available on all platforms.

    static VALUE
    proc_setpgrp(VALUE _)
    {
      /* check for posix setpgid() first; this matches the posix */
      /* getpgrp() above.  It appears that configure will set SETPGRP_VOID */
      /* even though setpgrp(0,0) would be preferred. The posix call avoids */
      /* this confusion. */
    #ifdef HAVE_SETPGID
        if (setpgid(0,0) < 0) rb_sys_fail(0);
    #elif defined(HAVE_SETPGRP) && defined(SETPGRP_VOID)
        if (setpgrp() < 0) rb_sys_fail(0);
    #endif
        return INT2FIX(0);
    }

setpriority(kind, integer, priority) → 0 click to toggle source

See `Process.getpriority`.

    Process.setpriority(Process::PRIO_USER, 0, 19)      #=> 0
    Process.setpriority(Process::PRIO_PROCESS, 0, 19)   #=> 0
    Process.getpriority(Process::PRIO_USER, 0)          #=> 19
    Process.getpriority(Process::PRIO_PROCESS, 0)       #=> 19

    static VALUE
    proc_setpriority(VALUE obj, VALUE which, VALUE who, VALUE prio)
    {
        int iwhich, iwho, iprio;

        iwhich = NUM2INT(which);
        iwho   = NUM2INT(who);
        iprio  = NUM2INT(prio);

        if (setpriority(iwhich, iwho, iprio) < 0)
            rb_sys_fail(0);
        return INT2FIX(0);
    }

setproctitle(string) → string click to toggle source

Sets the process title that appears on the ps(1) command. Not necessarily effective on all platforms. No exception will be raised regardless of the result, nor will `NotImplementedError` be raised even if the platform does not support the feature.

Calling this method does not affect the value of $0.

    Process.setproctitle('myapp: worker #%d' % worker_id)

This method first appeared in Ruby 2.1 to serve as a global variable free means to change the process title.

    static VALUE
    proc_setproctitle(VALUE process, VALUE title)
    {
        return ruby_setproctitle(title);
    }

setrlimit(resource, cur_limit, max_limit) → nil click to toggle source
setrlimit(resource, cur_limit) → nil

Sets the resource limit of the process. cur_limit means current (soft) limit and max_limit means maximum (hard) limit.

If max_limit is not given, cur_limit is used.

resource indicates the kind of resource to limit. It should be a symbol such as `:CORE`, a string such as `"CORE"` or a constant such as `Process::RLIMIT_CORE`. The available resources are OS dependent. Ruby may support following resources.

AS

  total available memory (bytes) (SUSv3, NetBSD, FreeBSD, OpenBSD but 4.4BSD-Lite)

CORE

  core size (bytes) (SUSv3)

CPU

  CPU time (seconds) (SUSv3)

DATA

  data segment (bytes) (SUSv3)

FSIZE

  file size (bytes) (SUSv3)

MEMLOCK

  total size for mlock(2) (bytes) (4.4BSD, GNU/Linux)

MSGQUEUE

  allocation for POSIX message queues (bytes) (GNU/Linux)

NICE

  ceiling on process's nice(2) value (number) (GNU/Linux)

NOFILE

  file descriptors (number) (SUSv3)

NPROC

  number of processes for the user (number) (4.4BSD, GNU/Linux)

RSS

  resident memory size (bytes) (4.2BSD, GNU/Linux)

RTPRIO

  ceiling on the process's real-time priority (number) (GNU/Linux)

RTTIME

  CPU time for real-time process (us) (GNU/Linux)

SBSIZE

  all socket buffers (bytes) (NetBSD, FreeBSD)

SIGPENDING

  number of queued signals allowed (signals) (GNU/Linux)

STACK

  stack size (bytes) (SUSv3)

cur_limit and max_limit may be `:INFINITY`, `"INFINITY"` or `Process::RLIM_INFINITY`, which means that the resource is not limited. They may be `Process::RLIM_SAVED_MAX`, `Process::RLIM_SAVED_CUR` and corresponding symbols and strings too. See system setrlimit(2) manual for details.

The following example raises the soft limit of core size to the hard limit to try to make core dump possible.

    Process.setrlimit(:CORE, Process.getrlimit(:CORE)[1])

    static VALUE
    proc_setrlimit(int argc, VALUE *argv, VALUE obj)
    {
        VALUE resource, rlim_cur, rlim_max;
        struct rlimit rlim;

        rb_check_arity(argc, 2, 3);
        resource = argv[0];
        rlim_cur = argv[1];
        if (argc < 3 || NIL_P(rlim_max = argv[2]))
            rlim_max = rlim_cur;

        rlim.rlim_cur = rlimit_resource_value(rlim_cur);
        rlim.rlim_max = rlimit_resource_value(rlim_max);

        if (setrlimit(rlimit_resource_type(resource), &rlim) < 0) {
            rb_sys_fail("setrlimit");
        }
        return Qnil;
    }

setsid → integer click to toggle source

Establishes this process as a new session and process group leader, with no controlling tty. Returns the session id. Not available on all platforms.

    Process.setsid   #=> 27422

    static VALUE
    proc_setsid(VALUE _)
    {
        rb_pid_t pid;

        pid = setsid();
        if (pid < 0) rb_sys_fail(0);
        return PIDT2NUM(pid);
    }

spawn([env,] command... [,options]) → pid click to toggle source
spawn([env,] command... [,options]) → pid

spawn executes specified command and return its pid.

    pid = spawn("tar xf ruby-2.0.0-p195.tar.bz2")
    Process.wait pid

    pid = spawn(RbConfig.ruby, "-eputs'Hello, world!'")
    Process.wait pid

This method is similar to `Kernel#system` but it doesn't wait for the command to finish.

The parent process should use `Process.wait` to collect the termination status of its child or use `Process.detach` to register disinterest in their status; otherwise, the operating system may accumulate zombie processes.

spawn has bunch of options to specify process attributes:

    env: hash
      name => val : set the environment variable
      name => nil : unset the environment variable

      the keys and the values except for +nil+ must be strings.
    command...:
      commandline                 : command line string which is passed to the standard shell
      cmdname, arg1, ...          : command name and one or more arguments (This form does not use the shell. See below for caveats.)
      [cmdname, argv0], arg1, ... : command name, argv[0] and zero or more arguments (no shell)
    options: hash
      clearing environment variables:
        :unsetenv_others => true   : clear environment variables except specified by env
        :unsetenv_others => false  : don't clear (default)
      process group:
        :pgroup => true or 0 : make a new process group
        :pgroup => pgid      : join the specified process group
        :pgroup => nil       : don't change the process group (default)
      create new process group: Windows only
        :new_pgroup => true  : the new process is the root process of a new process group
        :new_pgroup => false : don't create a new process group (default)
      resource limit: resourcename is core, cpu, data, etc.  See Process.setrlimit.
        :rlimit_resourcename => limit
        :rlimit_resourcename => [cur_limit, max_limit]
      umask:
        :umask => int
      redirection:
        key:
          FD              : single file descriptor in child process
          [FD, FD, ...]   : multiple file descriptor in child process
        value:
          FD                        : redirect to the file descriptor in parent process
          string                    : redirect to file with open(string, "r" or "w")
          [string]                  : redirect to file with open(string, File::RDONLY)
          [string, open_mode]       : redirect to file with open(string, open_mode, 0644)
          [string, open_mode, perm] : redirect to file with open(string, open_mode, perm)
          [:child, FD]              : redirect to the redirected file descriptor
          :close                    : close the file descriptor in child process
        FD is one of follows
          :in     : the file descriptor 0 which is the standard input
          :out    : the file descriptor 1 which is the standard output
          :err    : the file descriptor 2 which is the standard error
          integer : the file descriptor of specified the integer
          io      : the file descriptor specified as io.fileno
      file descriptor inheritance: close non-redirected non-standard fds (3, 4, 5, ...) or not
        :close_others => false  : inherit
      current directory:
        :chdir => str

The `cmdname, arg1, ...` form does not use the shell. However, on different OSes, different things are provided as built-in commands. An example of this is +'echo'+, which is a built-in on Windows, but is a normal program on Linux and Mac OS X. This means that `Process.spawn 'echo', '%Path%'` will display the contents of the `%Path%` environment variable on Windows, but `Process.spawn 'echo', '$PATH'` prints the literal `$PATH`.

If a hash is given as `env`, the environment is updated by `env` before `exec(2)` in the child process. If a pair in `env` has nil as the value, the variable is deleted.

    # set FOO as BAR and unset BAZ.
    pid = spawn({"FOO"=>"BAR", "BAZ"=>nil}, command)

If a hash is given as `options`, it specifies process group, create new process group, resource limit, current directory, umask and redirects for the child process. Also, it can be specified to clear environment variables.

The `:unsetenv_others` key in `options` specifies to clear environment variables, other than specified by `env`.

    pid = spawn(command, :unsetenv_others=>true) # no environment variable
    pid = spawn({"FOO"=>"BAR"}, command, :unsetenv_others=>true) # FOO only

The `:pgroup` key in `options` specifies a process group. The corresponding value should be true, zero, a positive integer, or nil. true and zero cause the process to be a process leader of a new process group. A non-zero positive integer causes the process to join the provided process group. The default value, nil, causes the process to remain in the same process group.

    pid = spawn(command, :pgroup=>true) # process leader
    pid = spawn(command, :pgroup=>10) # belongs to the process group 10

The `:new_pgroup` key in `options` specifies to pass `CREATE_NEW_PROCESS_GROUP` flag to `CreateProcessW()` that is Windows API. This option is only for Windows. true means the new process is the root process of the new process group. The new process has CTRL+C disabled. This flag is necessary for `Process.kill(:SIGINT, pid)` on the subprocess. :new_pgroup is false by default.

    pid = spawn(command, :new_pgroup=>true)  # new process group
    pid = spawn(command, :new_pgroup=>false) # same process group

The `:rlimit_`foo key specifies a resource limit. foo should be one of resource types such as `core`. The corresponding value should be an integer or an array which have one or two integers: same as cur_limit and max_limit arguments for `Process.setrlimit`.

    cur, max = Process.getrlimit(:CORE)
    pid = spawn(command, :rlimit_core=>[0,max]) # disable core temporary.
    pid = spawn(command, :rlimit_core=>max) # enable core dump
    pid = spawn(command, :rlimit_core=>0) # never dump core.

The `:umask` key in `options` specifies the umask.

    pid = spawn(command, :umask=>077)

The :in, :out, :err, an integer, an `IO` and an array key specifies a redirection. The redirection maps a file descriptor in the child process.

For example, stderr can be merged into stdout as follows:

    pid = spawn(command, :err=>:out)
    pid = spawn(command, 2=>1)
    pid = spawn(command, STDERR=>:out)
    pid = spawn(command, STDERR=>STDOUT)

The hash keys specifies a file descriptor in the child process started by spawn. :err, 2 and STDERR specifies the standard error stream (stderr).

The hash values specifies a file descriptor in the parent process which invokes spawn. :out, 1 and STDOUT specifies the standard output stream (stdout).

In the above example, the standard output in the child process is not specified. So it is inherited from the parent process.

The standard input stream (stdin) can be specified by :in, 0 and STDIN.

A filename can be specified as a hash value.

    pid = spawn(command, :in=>"/dev/null") # read mode
    pid = spawn(command, :out=>"/dev/null") # write mode
    pid = spawn(command, :err=>"log") # write mode
    pid = spawn(command, [:out, :err]=>"/dev/null") # write mode
    pid = spawn(command, 3=>"/dev/null") # read mode

For stdout and stderr (and combination of them), it is opened in write mode. Otherwise read mode is used.

For specifying flags and permission of file creation explicitly, an array is used instead.

    pid = spawn(command, :in=>["file"]) # read mode is assumed
    pid = spawn(command, :in=>["file", "r"])
    pid = spawn(command, :out=>["log", "w"]) # 0644 assumed
    pid = spawn(command, :out=>["log", "w", 0600])
    pid = spawn(command, :out=>["log", File::WRONLY|File::EXCL|File::CREAT, 0600])

The array specifies a filename, flags and permission. The flags can be a string or an integer. If the flags is omitted or nil, File::RDONLY is assumed. The permission should be an integer. If the permission is omitted or nil, 0644 is assumed.

If an array of IOs and integers are specified as a hash key, all the elements are redirected.

    # stdout and stderr is redirected to log file.
    # The file "log" is opened just once.
    pid = spawn(command, [:out, :err]=>["log", "w"])

Another way to merge multiple file descriptors is [:child, fd]. [:child, fd] means the file descriptor in the child process. This is different from fd. For example, :err=>:out means redirecting child stderr to parent stdout. But :err=>[:child, :out] means redirecting child stderr to child stdout. They differ if stdout is redirected in the child process as follows.

    # stdout and stderr is redirected to log file.
    # The file "log" is opened just once.
    pid = spawn(command, :out=>["log", "w"], :err=>[:child, :out])

[:child, :out] can be used to merge stderr into stdout in `IO.popen`. In this case, `IO.popen` redirects stdout to a pipe in the child process and [:child, :out] refers the redirected stdout.

    io = IO.popen(["sh", "-c", "echo out; echo err >&2", :err=>[:child, :out]])
    p io.read #=> "out\nerr\n"

The `:chdir` key in `options` specifies the current directory.

    pid = spawn(command, :chdir=>"/var/tmp")

spawn closes all non-standard unspecified descriptors by default. The “standard” descriptors are 0, 1 and 2. This behavior is specified by :close_others option. :close_others doesn't affect the standard descriptors which are closed only if :close is specified explicitly.

    pid = spawn(command, :close_others=>true)  # close 3,4,5,... (default)
    pid = spawn(command, :close_others=>false) # don't close 3,4,5,...

:close_others is false by default for spawn and `IO.popen`.

Note that fds which close-on-exec flag is already set are closed regardless of :close_others option.

So `IO.pipe` and spawn can be used as `IO.popen`.

    # similar to r = IO.popen(command)
    r, w = IO.pipe
    pid = spawn(command, :out=>w)   # r, w is closed in the child process.
    w.close

:close is specified as a hash value to close a fd individually.

    f = open(foo)
    system(command, f=>:close)        # don't inherit f.

If a file descriptor need to be inherited, io=>io can be used.

    # valgrind has --log-fd option for log destination.
    # log_w=>log_w indicates log_w.fileno inherits to child process.
    log_r, log_w = IO.pipe
    pid = spawn("valgrind", "--log-fd=#{log_w.fileno}", "echo", "a", log_w=>log_w)
    log_w.close
    p log_r.read

It is also possible to exchange file descriptors.

    pid = spawn(command, :out=>:err, :err=>:out)

The hash keys specify file descriptors in the child process. The hash values specifies file descriptors in the parent process. So the above specifies exchanging stdout and stderr. Internally, `spawn` uses an extra file descriptor to resolve such cyclic file descriptor mapping.

See `Kernel.exec` for the standard shell.

    static VALUE
    rb_f_spawn(int argc, VALUE *argv, VALUE _)
    {
        rb_pid_t pid;
        char errmsg[CHILD_ERRMSG_BUFLEN] = { '\0' };
        VALUE execarg_obj, fail_str;
        struct rb_execarg *eargp;

        execarg_obj = rb_execarg_new(argc, argv, TRUE, FALSE);
        eargp = rb_execarg_get(execarg_obj);
        fail_str = eargp->use_shell ? eargp->invoke.sh.shell_script : eargp->invoke.cmd.command_name;

        pid = rb_execarg_spawn(execarg_obj, errmsg, sizeof(errmsg));

        if (pid == -1) {
            int err = errno;
            rb_exec_fail(eargp, err, errmsg);
            RB_GC_GUARD(execarg_obj);
            rb_syserr_fail_str(err, fail_str);
        }
    #if defined(HAVE_WORKING_FORK) || defined(HAVE_SPAWNV)
        return PIDT2NUM(pid);
    #else
        return Qnil;
    #endif
    }

times → aProcessTms click to toggle source

Returns a `Tms` structure (see Process::Tms) that contains user and system CPU times for this process, and also for children processes.

    t = Process.times
    [ t.utime, t.stime, t.cutime, t.cstime ]   #=> [0.0, 0.02, 0.00, 0.00]

    VALUE
    rb_proc_times(VALUE obj)
    {
        VALUE utime, stime, cutime, cstime, ret;
    #if defined(RUSAGE_SELF) && defined(RUSAGE_CHILDREN)
        struct rusage usage_s, usage_c;

        if (getrusage(RUSAGE_SELF, &usage_s) != 0 || getrusage(RUSAGE_CHILDREN, &usage_c) != 0)
            rb_sys_fail("getrusage");
        utime = DBL2NUM((double)usage_s.ru_utime.tv_sec + (double)usage_s.ru_utime.tv_usec/1e6);
        stime = DBL2NUM((double)usage_s.ru_stime.tv_sec + (double)usage_s.ru_stime.tv_usec/1e6);
        cutime = DBL2NUM((double)usage_c.ru_utime.tv_sec + (double)usage_c.ru_utime.tv_usec/1e6);
        cstime = DBL2NUM((double)usage_c.ru_stime.tv_sec + (double)usage_c.ru_stime.tv_usec/1e6);
    #else
        const double hertz = (double)get_clk_tck();
        struct tms buf;

        times(&buf);
        utime = DBL2NUM(buf.tms_utime / hertz);
        stime = DBL2NUM(buf.tms_stime / hertz);
        cutime = DBL2NUM(buf.tms_cutime / hertz);
        cstime = DBL2NUM(buf.tms_cstime / hertz);
    #endif
        ret = rb_struct_new(rb_cProcessTms, utime, stime, cutime, cstime);
        RB_GC_GUARD(utime);
        RB_GC_GUARD(stime);
        RB_GC_GUARD(cutime);
        RB_GC_GUARD(cstime);
        return ret;
    }

uid → integer click to toggle source
Process::UID.rid → integer
Process::Sys.getuid → integer

Returns the (real) user ID of this process.

    Process.uid   #=> 501

    static VALUE
    proc_getuid(VALUE obj)
    {
        rb_uid_t uid = getuid();
        return UIDT2NUM(uid);
    }

uid= user → numeric click to toggle source

Sets the (user) user ID for this process. Not available on all platforms.

    static VALUE
    proc_setuid(VALUE obj, VALUE id)
    {
        rb_uid_t uid;

        check_uid_switch();

        uid = OBJ2UID(id);
    #if defined(HAVE_SETRESUID)
        if (setresuid(uid, -1, -1) < 0) rb_sys_fail(0);
    #elif defined HAVE_SETREUID
        if (setreuid(uid, -1) < 0) rb_sys_fail(0);
    #elif defined HAVE_SETRUID
        if (setruid(uid) < 0) rb_sys_fail(0);
    #elif defined HAVE_SETUID
        {
            if (geteuid() == uid) {
                if (setuid(uid) < 0) rb_sys_fail(0);
            }
            else {
                rb_notimplement();
            }
        }
    #endif
        return id;
    }

wait() → integer click to toggle source
wait(pid=-1, flags=0) → integer
waitpid(pid=-1, flags=0) → integer

Waits for a child process to exit, returns its process id, and sets `$?` to a `Process::Status` object containing information on that process. Which child it waits on depends on the value of pid:

> 0

  Waits for the child whose process ID equals pid.

0

  Waits for any child whose process group ID equals that of the calling process.

-1

  Waits for any child process (the default if no pid is given).

< -1

  Waits for any child whose process group ID equals the absolute value of pid.

The flags argument may be a logical or of the flag values `Process::WNOHANG` (do not block if no child available) or `Process::WUNTRACED` (return stopped children that haven't been reported). Not all flags are available on all platforms, but a flag value of zero will work on all platforms.

Calling this method raises a `SystemCallError` if there are no child processes. Not available on all platforms.

    include Process
    fork { exit 99 }                 #=> 27429
    wait                             #=> 27429
    $?.exitstatus                    #=> 99

    pid = fork { sleep 3 }           #=> 27440
    Time.now                         #=> 2008-03-08 19:56:16 +0900
    waitpid(pid, Process::WNOHANG)   #=> nil
    Time.now                         #=> 2008-03-08 19:56:16 +0900
    waitpid(pid, 0)                  #=> 27440
    Time.now                         #=> 2008-03-08 19:56:19 +0900

    static VALUE
    proc_m_wait(int c, VALUE *v, VALUE _)
    {
        return proc_wait(c, v);
    }

wait2(pid=-1, flags=0) → [pid, status] click to toggle source
waitpid2(pid=-1, flags=0) → [pid, status]

Waits for a child process to exit (see `Process::waitpid` for exact semantics) and returns an array containing the process id and the exit status (a `Process::Status` object) of that child. Raises a `SystemCallError` if there are no child processes.

    Process.fork { exit 99 }   #=> 27437
    pid, status = Process.wait2
    pid                        #=> 27437
    status.exitstatus          #=> 99

    static VALUE
    proc_wait2(int argc, VALUE *argv, VALUE _)
    {
        VALUE pid = proc_wait(argc, argv);
        if (NIL_P(pid)) return Qnil;
        return rb_assoc_new(pid, rb_last_status_get());
    }

waitall → [ [pid1,status1], ...] click to toggle source

Waits for all children, returning an array of pid/status pairs (where status is a `Process::Status` object).

    fork { sleep 0.2; exit 2 }   #=> 27432
    fork { sleep 0.1; exit 1 }   #=> 27433
    fork {            exit 0 }   #=> 27434
    p Process.waitall

produces:

    [[30982, #<Process::Status: pid 30982 exit 0>],
     [30979, #<Process::Status: pid 30979 exit 1>],
     [30976, #<Process::Status: pid 30976 exit 2>]]

    static VALUE
    proc_waitall(VALUE _)
    {
        VALUE result;
        rb_pid_t pid;
        int status;

        result = rb_ary_new();
        rb_last_status_clear();

        for (pid = -1;;) {
            pid = rb_waitpid(-1, &status, 0);
            if (pid == -1) {
                int e = errno;
                if (e == ECHILD)
                    break;
                rb_syserr_fail(e, 0);
            }
            rb_ary_push(result, rb_assoc_new(PIDT2NUM(pid), rb_last_status_get()));
        }
        return result;
    }

wait() → integer click to toggle source
wait(pid=-1, flags=0) → integer
waitpid(pid=-1, flags=0) → integer

Waits for a child process to exit, returns its process id, and sets `$?` to a `Process::Status` object containing information on that process. Which child it waits on depends on the value of pid:

> 0

  Waits for the child whose process ID equals pid.

0

  Waits for any child whose process group ID equals that of the calling process.

-1

  Waits for any child process (the default if no pid is given).

< -1

  Waits for any child whose process group ID equals the absolute value of pid.

The flags argument may be a logical or of the flag values `Process::WNOHANG` (do not block if no child available) or `Process::WUNTRACED` (return stopped children that haven't been reported). Not all flags are available on all platforms, but a flag value of zero will work on all platforms.

Calling this method raises a `SystemCallError` if there are no child processes. Not available on all platforms.

    include Process
    fork { exit 99 }                 #=> 27429
    wait                             #=> 27429
    $?.exitstatus                    #=> 99

    pid = fork { sleep 3 }           #=> 27440
    Time.now                         #=> 2008-03-08 19:56:16 +0900
    waitpid(pid, Process::WNOHANG)   #=> nil
    Time.now                         #=> 2008-03-08 19:56:16 +0900
    waitpid(pid, 0)                  #=> 27440
    Time.now                         #=> 2008-03-08 19:56:19 +0900

    static VALUE
    proc_m_wait(int c, VALUE *v, VALUE _)
    {
        return proc_wait(c, v);
    }

wait2(pid=-1, flags=0) → [pid, status] click to toggle source
waitpid2(pid=-1, flags=0) → [pid, status]

Waits for a child process to exit (see `Process::waitpid` for exact semantics) and returns an array containing the process id and the exit status (a `Process::Status` object) of that child. Raises a `SystemCallError` if there are no child processes.

    Process.fork { exit 99 }   #=> 27437
    pid, status = Process.wait2
    pid                        #=> 27437
    status.exitstatus          #=> 99

    static VALUE
    proc_wait2(int argc, VALUE *argv, VALUE _)
    {
        VALUE pid = proc_wait(argc, argv);
        if (NIL_P(pid)) return Qnil;
        return rb_assoc_new(pid, rb_last_status_get());
    }