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e23e52a8e9
Harmonizes the option listing including formatting in a similar manner to the synopsis of each entry.
40 lines
1.8 KiB
ReStructuredText
40 lines
1.8 KiB
ReStructuredText
.. _cmd-psub:
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psub - perform process substitution
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===================================
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Synopsis
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--------
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.. synopsis::
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COMMAND1 ( COMMAND2 | psub [-F | --fifo] [-f | --file] [(-s | --suffix) SUFFIX] )
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Description
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-----------
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Some shells (e.g., ksh, bash) feature a syntax that is a mix between command substitution and piping, called process substitution. It is used to send the output of a command into the calling command, much like command substitution, but with the difference that the output is not sent through commandline arguments but through a named pipe, with the filename of the named pipe sent as an argument to the calling program. ``psub`` combined with a regular command substitution provides the same functionality.
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The following options are available:
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**-f** or **--file**
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Use a regular file instead of a named pipe to communicate with the calling process. This will cause ``psub`` to be significantly slower when large amounts of data are involved, but has the advantage that the reading process can seek in the stream. This is the default.
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**-F** or **--fifo**
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Use a named pipe rather than a file. You should only use this if the command produces no more than 8 KiB of output. The limit on the amount of data a FIFO can buffer varies with the OS but is typically 8 KiB, 16 KiB or 64 KiB. If you use this option and the command on the left of the psub pipeline produces more output a deadlock is likely to occur.
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**-s** or **--suffix** *SUFFIX*
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Append SUFFIX to the filename.
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Example
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-------
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::
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diff (sort a.txt | psub) (sort b.txt | psub)
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# shows the difference between the sorted versions of files ``a.txt`` and ``b.txt``.
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source-highlight -f esc (cpp main.c | psub -f -s .c)
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# highlights ``main.c`` after preprocessing as a C source.
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