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20 lines
No EOL
1.1 KiB
Text
20 lines
No EOL
1.1 KiB
Text
\section psub psub - perform process substitution
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\subsection psub-synopsis Synopsis
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\fish{synopsis}
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COMMAND1 ( COMMAND2 | psub [-f] )
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\endfish
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\subsection psub-description Description
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Posix shells 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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If the `-f` or `--file` switch is given to `psub`, `psub` will 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.
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\subsection psub-example Example
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\fish
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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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\endfish |