exec(1p) — Linux manual page

EXEC(1P)                POSIX Programmer's Manual               EXEC(1P)

PROLOG

       This manual page is part of the POSIX Programmer's Manual.  The
       Linux implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior),
       or the interface may not be implemented on Linux.

NAME

       exec — execute commands and open, close, or copy file descriptors

SYNOPSIS

       exec [command [argument...]]

DESCRIPTION

       The exec utility shall open, close, and/or copy file descriptors
       as specified by any redirections as part of the command.

       If exec is specified without command or arguments, and any file
       descriptors with numbers greater than 2 are opened with
       associated redirection statements, it is unspecified whether
       those file descriptors remain open when the shell invokes another
       utility.  Scripts concerned that child shells could misuse open
       file descriptors can always close them explicitly, as shown in
       one of the following examples.

       If exec is specified with command, it shall replace the shell
       with command without creating a new process. If arguments are
       specified, they shall be arguments to command.  Redirection
       affects the current shell execution environment.

OPTIONS

       None.

OPERANDS

       See the DESCRIPTION.

STDIN

       Not used.

INPUT FILES

       None.

ENVIRONMENT VARIABLES

       None.

ASYNCHRONOUS EVENTS

       Default.

STDOUT

       Not used.

STDERR

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES

       None.

EXTENDED DESCRIPTION

       None.

EXIT STATUS

       If command is specified, exec shall not return to the shell;
       rather, the exit status of the process shall be the exit status
       of the program implementing command, which overlaid the shell. If
       command is not found, the exit status shall be 127. If command is
       found, but it is not an executable utility, the exit status shall
       be 126. If a redirection error occurs (see Section 2.8.1,
       Consequences of Shell Errors), the shell shall exit with a value
       in the range 1-125. Otherwise, exec shall return a zero exit
       status.

CONSEQUENCES OF ERRORS

       Default.

       The following sections are informative.

APPLICATION USAGE

       None.

EXAMPLES

       Open readfile as file descriptor 3 for reading:

           exec 3< readfile

       Open writefile as file descriptor 4 for writing:

           exec 4> writefile

       Make file descriptor 5 a copy of file descriptor 0:

           exec 5<&0

       Close file descriptor 3:

           exec 3<&-

       Cat the file maggie by replacing the current shell with the cat
       utility:

           exec cat maggie

RATIONALE

       Most historical implementations were not conformant in that:

           foo=bar exec cmd

       did not pass foo to cmd.

FUTURE DIRECTIONS

       None.

SEE ALSO

       Section 2.14, Special Built-In Utilities

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  In the event of any
       discrepancy between this version and the original IEEE and The
       Open Group Standard, the original IEEE and The Open Group
       Standard is the referee document. The original Standard can be
       obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page
       are most likely to have been introduced during the conversion of
       the source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group               2017                          EXEC(1P)

Pages that refer to this page: fcntl.h(0p), stdarg.h(0p), unistd.h(0p), awk(1p), c99(1p), command(1p), fort77(1p), make(1p), newgrp(1p), sh(1p), xargs(1p), aio_error(3p), aio_read(3p), aio_return(3p), aio_write(3p), alarm(3p), atexit(3p), chmod(3p), close(3p), confstr(3p), environ(3p), exit(3p), fcntl(3p), fexecve(3p), fork(3p), fstatvfs(3p), getenv(3p), getitimer(3p), getopt(3p), getpgid(3p), getpgrp(3p), getpid(3p), getppid(3p), getrlimit(3p), getsid(3p), glob(3p), lio_listio(3p), mknod(3p), mlock(3p), mlockall(3p), mmap(3p), nice(3p), open(3p), posix_spawn(3p), posix_trace_create(3p), posix_trace_event(3p), posix_trace_eventid_equal(3p), posix_typed_mem_open(3p), pthread_atfork(3p), pthread_sigmask(3p), putenv(3p), readdir(3p), semop(3p), setegid(3p), setenv(3p), seteuid(3p), setgid(3p), setlocale(3p), setpgid(3p), setpgrp(3p), setregid(3p), setuid(3p), shmat(3p), shmdt(3p), shm_open(3p), sigaction(3p), sigaltstack(3p), sighold(3p), signal(3p), sigpending(3p), system(3p), times(3p), ulimit(3p), umask(3p), wait(3p), waitid(3p), wordexp(3p)

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