Mirrors/fish-shell
2
0
Fork 0
mirror of https://github.com/fish-shell/fish-shell synced 2024-12-28 05:43:11 +00:00
Code Issues Projects Releases Packages Wiki Activity

Revise "Piping" section

Browse source
This commit is contained in:
Matthew Dutson 2021-01-12 17:24:23 -06:00
parent 0136db0a22
commit 480f7fdb37
1 changed files with 10 additions and 15 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

25
doc_src/index.rst
View file

@ -104,7 +104,7 @@ Syntax Overview
Shells like fish are used by giving them commands. Every fish command follows the same basic syntax. A command is executed by writing the name of the command followed by any arguments. For example::
echo hello world
echo hello world
This calls the :ref:`echo <cmd-echo>` command. ``echo`` writes its arguments to the screen. In the example above, the output is ``hello world``. Everything in fish is done with commands. There are commands for repeating other commands, commands for assigning variables, commands for treating a group of commands as a single command, etc. All of these commands follow the same basic syntax.
@ -164,19 +164,19 @@ Single quotes have no special meaning within double quotes and vice versa.
Example::
rm "cumbersome filename.txt"
rm "cumbersome filename.txt"
removes the file ``cumbersome filename.txt``, while
::
rm cumbersome filename.txt
rm cumbersome filename.txt
removes two files, ``cumbersome`` and ``filename.txt``.
Another example::
grep 'enabled)$' foo.txt
grep 'enabled)$' foo.txt
searches for lines ending in ``enabled)`` in ``foo.txt`` (the ``$`` is special to ``grep``: it matches the end of the line).
@ -280,24 +280,19 @@ For example, ``echo hello 2> output.stderr`` writes the standard error (file des
Piping
------
Another way to redirect streams is a *pipe*. This connects streams with each other, usually the standard output of one command with the standard input of another.
Another way to redirect streams is a *pipe*. A pipe connects streams with each other. Usually the standard output of one command is connected with the standard input of another. This is done by separating commands with the pipe character ``|``. For example::
This is done by separating the commands by the pipe character ``|``. For example
cat foo.txt | head
::
The command ``cat foo.txt`` sends the contents of ``foo.txt`` to stdout. This output is provided as input for the ``head`` program, which prints the first 10 lines of its input.
cat foo.txt | head
will call the ``cat`` program with the parameter 'foo.txt', which will print the contents of the file 'foo.txt'. The contents of foo.txt will then be sent to the 'head' program, which will write the first few lines it reads to its output - the screen.
It is possible to use a different output file descriptor by prepending its FD number and then output redirect symbol to the pipe. For example::
make fish 2>| less
It is possible to pipe a different output file descriptor by prepending its FD number and the output redirect symbol to the pipe. For example::
make fish 2>| less
will attempt to build ``fish``, and any errors will be shown using the ``less`` pager. [#]_
As a convenience, the pipe ``&|`` redirects both stdout and stderr to the same process. (Note this is different from bash, which uses ``|&``).
As a convenience, the pipe ``&|`` redirects both stdout and stderr to the same process. Note that this is different from bash, which uses ``|&``.
.. [#] A "pager" here is a program that takes output and "paginates" it. ``less`` doesn't just do pages, it allows arbitrary scrolling (even back!).