2004-11-03 13:51:07 +00:00
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.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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2007-06-20 22:33:04 +00:00
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.TH "EXEC" 1P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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2004-11-03 13:51:07 +00:00
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.\" exec
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2007-09-20 06:03:25 +00:00
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.SH PROLOG
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This manual page is part of the POSIX Programmer's Manual.
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The Linux implementation of this interface may differ (consult
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the corresponding Linux manual page for details of Linux behavior),
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or the interface may not be implemented on Linux.
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2004-11-03 13:51:07 +00:00
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.SH NAME
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exec \- execute commands and open, close, or copy file descriptors
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.SH SYNOPSIS
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.LP
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\fBexec\fP \fB[\fP\fIcommand\fP \fB[\fP\fIargument\fP \fB...\fP\fB]]\fP
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.SH DESCRIPTION
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.LP
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The \fIexec\fP utility shall open, close, and/or copy file descriptors
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as specified by any redirections as part of the
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command.
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.LP
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If \fIexec\fP is specified without \fIcommand\fP or \fIargument\fPs,
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and any file descriptors with numbers greater than 2 are
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opened with associated redirection statements, it is unspecified whether
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those file descriptors remain open when the shell invokes
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another utility. Scripts concerned that child shells could misuse
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open file descriptors can always close them explicitly, as shown
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in one of the following examples.
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.LP
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If \fIexec\fP is specified with \fIcommand\fP, it shall replace the
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shell with \fIcommand\fP without creating a new process.
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If \fIargument\fPs are specified, they shall be arguments to \fIcommand\fP.
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Redirection affects the current shell execution
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environment.
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.SH OPTIONS
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.LP
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None.
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.SH OPERANDS
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.LP
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See the DESCRIPTION.
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.SH STDIN
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.LP
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Not used.
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.SH INPUT FILES
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.LP
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None.
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.SH ENVIRONMENT VARIABLES
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.LP
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None.
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.SH ASYNCHRONOUS EVENTS
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.LP
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Default.
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.SH STDOUT
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.LP
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Not used.
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.SH STDERR
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.LP
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The standard error shall be used only for diagnostic messages.
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.SH OUTPUT FILES
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.LP
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None.
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.SH EXTENDED DESCRIPTION
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.LP
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None.
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.SH EXIT STATUS
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.LP
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If \fIcommand\fP is specified, \fIexec\fP shall not return to the
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shell; rather, the exit status of the process shall be the
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exit status of the program implementing \fIcommand\fP, which overlaid
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the shell. If \fIcommand\fP is not found, the exit status
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shall be 127. If \fIcommand\fP is found, but it is not an executable
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utility, the exit status shall be 126. If a redirection error
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occurs (see \fIConsequences of Shell Errors\fP ), the shell shall
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exit with a value in
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the range 1-125. Otherwise, \fIexec\fP shall return a zero exit status.
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.SH CONSEQUENCES OF ERRORS
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.LP
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Default.
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.LP
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\fIThe following sections are informative.\fP
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.SH APPLICATION USAGE
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.LP
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None.
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.SH EXAMPLES
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.LP
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Open \fIreadfile\fP as file descriptor 3 for reading:
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.sp
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.RS
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.nf
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\fBexec 3< readfile
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\fP
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.fi
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.RE
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.LP
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Open \fIwritefile\fP as file descriptor 4 for writing:
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.sp
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.RS
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.nf
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\fBexec 4> writefile
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\fP
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.fi
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.RE
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.LP
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Make file descriptor 5 a copy of file descriptor 0:
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.sp
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.RS
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.nf
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\fBexec 5<&0
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\fP
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.fi
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.RE
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.LP
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Close file descriptor 3:
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.sp
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.RS
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.nf
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\fBexec 3<&-
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\fP
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.fi
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.RE
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.LP
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Cat the file \fBmaggie\fP by replacing the current shell with the
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\fIcat\fP utility:
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.sp
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.RS
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.nf
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\fBexec cat maggie
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\fP
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.fi
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.RE
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.SH RATIONALE
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.LP
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Most historical implementations were not conformant in that:
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.sp
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.RS
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.nf
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\fBfoo=bar exec cmd
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\fP
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.fi
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.RE
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.LP
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did not pass \fBfoo\fP to \fBcmd\fP.
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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\fISpecial Built-In Utilities\fP
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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