PROLOG<\/a> This manual page is part of the POSIX Programmer\u2019s 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.<\/p>\n exec \u2014 execute commands and open, close, or copy file descriptors<\/p>\n exec [<\/b>command<\/i> [<\/b>argument<\/i>…]]<\/b><\/p>\n The exec<\/i> utility shall open, close, and\/or copy file descriptors as specified by any redirections as part of the command.<\/p>\n If exec<\/i> is specified without command<\/i> or argument<\/i>s, 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.<\/p>\n If exec<\/i> is specified with command<\/i>, it shall replace the shell with command<\/i> without creating a new process. If argument<\/i>s are specified, they shall be arguments to command<\/i>. Redirection affects the current shell execution environment.<\/p>\n None.<\/p>\n See the DESCRIPTION.<\/p>\n Not used.<\/p>\n None.<\/p>\n None.<\/p>\n Default.<\/p>\n Not used.<\/p>\n The standard error shall be used only for diagnostic messages.<\/p>\n None.<\/p>\n None.<\/p>\n If command<\/i> is specified, exec<\/i> shall not return to the shell; rather, the exit status of the process shall be the exit status of the program implementing command<\/i>, which overlaid the shell. If command<\/i> is not found, the exit status shall be 127. If command<\/i> 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<\/i>, Consequences of Shell Errors<\/i>), the shell shall exit with a value in the range 1\u2212125. Otherwise, exec<\/i> shall return a zero exit status.<\/p>\n Default.<\/p>\n The following sections are informative.<\/i><\/p>\n None.<\/p>\n Open readfile<\/i> as file descriptor 3 for reading:<\/p>\n exec 3< readfile<\/p>\n Open writefile<\/i> as file descriptor 4 for writing:<\/p>\n exec 4> writefile<\/p>\n Make file descriptor 5 a copy of file descriptor 0:<\/p>\n exec 5<&0<\/p>\n Close file descriptor 3:<\/p>\n exec 3<&-<\/p>\n Cat the file maggie<\/b> by replacing the current shell with the cat<\/i> utility:<\/p>\n exec cat maggie<\/p>\n Most historical implementations were not conformant in that:<\/p>\n foo=bar exec cmd<\/p>\n did not pass foo<\/b> to cmd<\/b>.<\/p>\n None.<\/p>\n
NAME<\/a>
SYNOPSIS<\/a>
DESCRIPTION<\/a>
OPTIONS<\/a>
OPERANDS<\/a>
STDIN<\/a>
INPUT FILES<\/a>
ENVIRONMENT VARIABLES<\/a>
ASYNCHRONOUS EVENTS<\/a>
STDOUT<\/a>
STDERR<\/a>
OUTPUT FILES<\/a>
EXTENDED DESCRIPTION<\/a>
EXIT STATUS<\/a>
CONSEQUENCES OF ERRORS<\/a>
APPLICATION USAGE<\/a>
EXAMPLES<\/a>
RATIONALE<\/a>
FUTURE DIRECTIONS<\/a>
SEE ALSO<\/a>
COPYRIGHT<\/a> <\/p>\n
\nPROLOG <\/a> <\/h2>\n
NAME <\/a> <\/h2>\n
SYNOPSIS <\/a> <\/h2>\n
DESCRIPTION <\/a> <\/h2>\n
OPTIONS <\/a> <\/h2>\n
OPERANDS <\/a> <\/h2>\n
STDIN <\/a> <\/h2>\n
INPUT FILES <\/a> <\/h2>\n
ENVIRONMENT VARIABLES <\/a> <\/h2>\n
ASYNCHRONOUS EVENTS <\/a> <\/h2>\n
STDOUT <\/a> <\/h2>\n
STDERR <\/a> <\/h2>\n
OUTPUT FILES <\/a> <\/h2>\n
EXTENDED DESCRIPTION <\/a> <\/h2>\n
EXIT STATUS <\/a> <\/h2>\n
CONSEQUENCES OF ERRORS <\/a> <\/h2>\n
APPLICATION USAGE <\/a> <\/h2>\n
EXAMPLES <\/a> <\/h2>\n
RATIONALE <\/a> <\/h2>\n
FUTURE DIRECTIONS <\/a> <\/h2>\n
SEE ALSO <\/a> <\/h2>\n