trusty (1) exec.1posix.gz

Provided by: manpages-posix_2.16-1_all bug

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 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

       Special Built-In Utilities

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
       Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open  Group  Base
       Specifications Issue 6, Copyright (C) 2001-2003 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 .