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GNU macro processor

12.1 Executing simple commands

Any shell command can be executed, using syscmd:

syscmd(shell-command)

which executes shell-command as a shell command.

The expansion of syscmd is void, not the output from shell-command! Output or error messages from shell-command are not read by m4. See section 12.2 Reading the output of commands if you need to process the command output.

Prior to executing the command, m4 flushes its output buffers. The default standard input, output and error of shell-command are the same as those of m4.

The builtin macro syscmd is recognized only when given arguments.