mirror of
https://github.com/fish-shell/fish-shell.git
synced 2024-11-23 10:00:43 +08:00
38b24c2325
This makes it so we link to the very top of the document instead of a special anchor we manually include. So clicking e.g. :doc:`string <cmds/string>` will link you to cmds/string.html instead of cmds/string.html#cmd-string. I would love to have a way to say "this document from the root of the document path", but that doesn't appear to work, I tried `/cmds/string`. So we'll just have to use cmds/string in normal documents and plain `string` from other commands.
107 lines
4.0 KiB
ReStructuredText
107 lines
4.0 KiB
ReStructuredText
.. _cmd-printf:
|
|
|
|
printf - display text according to a format string
|
|
==================================================
|
|
|
|
Synopsis
|
|
--------
|
|
|
|
.. synopsis::
|
|
|
|
printf FORMAT [ARGUMENT ...]
|
|
|
|
Description
|
|
-----------
|
|
|
|
.. only:: builder_man
|
|
|
|
NOTE: This page documents the fish builtin ``printf``.
|
|
To see the documentation on the ``printf`` command you might have,
|
|
use ``command man printf``.
|
|
|
|
``printf`` uses the format string *FORMAT* to print the *ARGUMENT* arguments. This means that it takes format specifiers in the format string and replaces each with an argument.
|
|
|
|
The *FORMAT* argument is re-used as many times as necessary to convert all of the given arguments. So ``printf %s\n flounder catfish clownfish shark`` will print four lines.
|
|
|
|
Unlike :doc:`echo <echo>`, ``printf`` does not append a new line unless it is specified as part of the string.
|
|
|
|
It doesn't support any options, so there is no need for a ``--`` separator, which makes it easier to use for arbitrary input than ``echo``. [#]_
|
|
|
|
Format Specifiers
|
|
-----------------
|
|
Valid format specifiers are taken from the C library function ``printf(3)``:
|
|
|
|
- ``%d`` or ``%i``: Argument will be used as decimal integer (signed or unsigned)
|
|
|
|
- ``%o``: An octal unsigned integer
|
|
|
|
- ``%u``: An unsigned decimal integer - this means negative numbers will wrap around
|
|
|
|
- ``%x`` or ``%X``: An unsigned hexadecimal integer
|
|
|
|
- ``%f``, ``%g`` or ``%G``: A floating-point number. ``%f`` defaults to 6 places after the decimal point (which is locale-dependent - e.g. in de_DE it will be a ``,``). ``%g`` and ``%G`` will trim trailing zeroes and switch to scientific notation (like ``%e``) if the numbers get small or large enough.
|
|
|
|
- ``%e`` or ``%E``: A floating-point number in scientific (XXXeYY) notation
|
|
|
|
- ``%s``: A string
|
|
|
|
- ``%b``: As a string, interpreting backslash escapes, except that octal escapes are of the form \0 or \0ooo.
|
|
|
|
``%%`` signifies a literal "%".
|
|
|
|
Conversion can fail, e.g. "102.234" can't losslessly convert to an integer, causing printf to print an error. If you are okay with losing information, silence errors with ``2>/dev/null``.
|
|
|
|
A number between the ``%`` and the format letter specifies the width. The result will be left-padded with spaces.
|
|
|
|
Backslash Escapes
|
|
-----------------
|
|
printf also knows a number of backslash escapes:
|
|
|
|
- ``\"`` double quote
|
|
- ``\\`` backslash
|
|
- ``\a`` alert (bell)
|
|
- ``\b`` backspace
|
|
- ``\c`` produce no further output
|
|
- ``\e`` escape
|
|
- ``\f`` form feed
|
|
- ``\n`` new line
|
|
- ``\r`` carriage return
|
|
- ``\t`` horizontal tab
|
|
- ``\v`` vertical tab
|
|
- ``\ooo`` octal number (ooo is 1 to 3 digits)
|
|
- ``\xhh`` hexadecimal number (hhh is 1 to 2 digits)
|
|
- ``\uhhhh`` 16-bit Unicode character (hhhh is 4 digits)
|
|
- ``\Uhhhhhhhh`` 32-bit Unicode character (hhhhhhhh is 8 digits)
|
|
|
|
Errors and Return Status
|
|
------------------------
|
|
If the given argument doesn't work for the given format (like when you try to convert a number like 3.141592 to an integer), printf prints an error, to stderr. printf will then also return non-zero, but will still try to print as much as it can.
|
|
|
|
It will also return non-zero if no argument at all was given, in which case it will print nothing.
|
|
|
|
This printf has been imported from the printf in GNU Coreutils version 6.9. If you would like to use a newer version of printf, for example the one shipped with your OS, try ``command printf``.
|
|
|
|
Example
|
|
-------
|
|
|
|
::
|
|
|
|
printf '%s\t%s\n' flounder fish
|
|
|
|
Will print "flounder fish" (separated with a tab character), followed by a newline character. This is useful for writing completions, as fish expects completion scripts to output the option followed by the description, separated with a tab character.
|
|
|
|
::
|
|
|
|
printf '%s: %d' "Number of bananas in my pocket" 42
|
|
|
|
Will print "Number of bananas in my pocket: 42", `without` a newline.
|
|
|
|
See Also
|
|
--------
|
|
|
|
- the :doc:`echo <echo>` command, for simpler output
|
|
|
|
Footnotes
|
|
---------
|
|
.. [#] In fact, while fish's ``echo`` supports ``--``, POSIX forbids it, so other implementations can't be used if the input contains anything starting with ``-``.
|