fish-shell/doc_src/psub.txt
Mark Griffiths 509d152e54 Tutorial auto colouring, Man page and Make fixes
Completely fixes #1557 and the underlying Doxygen changes that caused
it. Should make fish docs simpler and more robust, more consistent and
generally prettier.

todo:
- trap unmarked text as arguments in context
- test & fix sed portability - see in particular. (so far tested on BSD
(Mac) and GNU sed).
- test Makefile changes
- last round of aesthetic changes and getting that ascii fish in there…
2014-09-03 14:43:26 +01:00

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\section psub psub - perform process substitution
\subsection psub-synopsis Synopsis
\fish{synopsis}
COMMAND1 (COMMAND2 | psub [-f])
\endfish
\subsection psub-description Description
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.
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.
\subsection psub-example Example
\fish
diff (sort a.txt | psub) (sort b.txt | psub)
# shows the difference between the sorted versions of files `a.txt` and `b.txt`.
\endfish