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