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. exec — execute commands and open, close, or copy file descriptors exec [command [argument...]] The utility shall open, close, and/or copy file descriptors as specified by any redirections as part of the command. If is specified without or 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 is specified with it shall replace the shell with without creating a new process. If are specified, they shall be arguments to Redirection affects the current shell execution environment. None. See the DESCRIPTION. Not used. None. None. Default. Not used. The standard error shall be used only for diagnostic messages. None. None. If is specified, shall not return to the shell; rather, the exit status of the process shall be the exit status of the program implementing which overlaid the shell. If is not found, the exit status shall be 127. If is found, but it is not an executable utility, the exit status shall be 126. If a redirection error occurs (see the shell shall exit with a ‐2‐ value in the range 1−125. Otherwise, shall return a zero exit status. Default. None. Open as file descriptor 3 for reading: exec 3< readfile Open 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 by replacing the current shell with the utility: exec cat maggie Most historical implementations were not conformant in that: foo=bar exec cmd did not pass to None. Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology ‐‐ Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. (This is POSIX.1‐2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/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 .