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GNU macro processor

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12.4 Making names for temporary files

Commands specified to syscmd or esyscmd might need a temporary file, for output or for some other purpose. There is a builtin macro, maketemp, for making temporary file names:

 
maketemp(template)

which expands to a name of a non-existent file, made from the string template, which should end with the string `XXXXXX'. The six X's are then replaced, usually with something that includes the process id of the m4 process, in order to make the filename unique.

 
maketemp(`/tmp/fooXXXXXX')
=>/tmp/fooa07346
maketemp(`/tmp/fooXXXXXX')
=>/tmp/fooa07346

As seen in the example, several calls of maketemp might expand to the same string, since the selection criteria is whether the file exists or not. If a file has not been created before the next call, the two macro calls might expand to the same name.

The builtin macro maketemp is recognized only when given arguments.


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