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02d82dcf85
Adds synopses for those commands missing them. Moves all synopsis sections to code blocks. This improves the appearance, although highlighting as fish code may not be the ideal appearance.
36 lines
1.8 KiB
ReStructuredText
36 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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::
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COMMAND1 ( COMMAND2 | psub [-F | --fifo] [-f | --file] [-s 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`` will cause psub to 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`` will cause psub to 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`` will 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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