(m4.info)Shell commands

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13 Macros for running shell commands
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There are a few builtin macros in 'm4' that allow you to run shell
commands from within 'm4'.

   Note that the definition of a valid shell command is system
dependent.  On UNIX systems, this is the typical '/bin/sh'.  But on
other systems, such as native Windows, the shell has a different syntax
of commands that it understands.  Some examples in this chapter assume
'/bin/sh', and also demonstrate how to quit early with a known exit
value if this is not the case.

Platform macros

Determining the platform

Syscmd

Executing simple commands

Esyscmd

Reading the output of commands

Sysval

Exit status

Mkstemp

Making temporary files