hyperreal/bash-hackers-wiki
1
0
Fork 0
mirror of https://github.com/flokoe/bash-hackers-wiki.git synced 2024-11-25 15:53:41 +01:00
Code Issues Actions Packages Projects Releases Wiki Activity
cea8224acf
bash-hackers-wiki/docs/commands/builtin/echo.md

87 lines
3.5 KiB
Markdown
Raw Normal View History

Convert all builtin commands to Markdown
2023-07-05 10:53:12 +02:00
# The echo builtin command
## Synopsis
echo [-neE] [arg ...]
## Description
format(docs): remove escaped 's character pairs
2024-03-30 19:22:45 +01:00
`echo` outputs it's args to stdout, separated by spaces, followed by a
Convert all builtin commands to Markdown
2023-07-05 10:53:12 +02:00
newline. The return status is always `0`. If the
Fix hyperlinks of markdown pages at depth 3 find docs/ -depth 3 -name '*.md' | xargs grep '(.*/' -l | \ xargs -I{} \ sed -i '' \ -e 's%(/\([^/#).][^/#).]*\)/\([^/#).][^/#).]*\)\(.md\)\{0\})%(../../\1/\2.md)%g' \ -e 's%(/\([^/#).][^/#).]*\)/\([^/#).][^/#).]*\)#\([a-zA-Z_-][0-9a-zA-Z_-]*\))%(../../\1/\2.md#\3)%g' \ -e 's%(/\([^/#).][^/#).]*\)/\([^/#).][^/#).]*\)/\([^/#).][^/#).]*\)\(.md\)\{0\})%(../../\1/\2/\3.md)%g' \ -e 's%(/\([^/#).][^/#).]*\)/\([^/#).][^/#).]*\)/\([^/#).][^/#).]*\)#\([a-zA-Z_-][0-9a-zA-Z_-]*\))%(../../\1/\2/\3.md#\4)%g' \ -e 's%](\([^:.>)#][^:.>)#]*\))%](../../\1.md)%g' \ -e 's%](\([^:.>)#][^:.>)#]*\)#\([^:.>)#][^:.>)#]*\))%](../../\1.md#\2)%g' \ {} Related to https://github.com/flokoe/bash-hackers-wiki/issues/10
2024-01-29 02:07:56 +01:00
[shopt](../../commands/builtin/shopt.md) option `xpg_echo` is set, Bash
Convert all builtin commands to Markdown
2023-07-05 10:53:12 +02:00
dynamically determines whether echo should expand escape characters
format(docs): remove escaped t's
2024-03-30 20:09:26 +01:00
(listed below) by default based on the current platform. `echo` doesn't
Convert all builtin commands to Markdown
2023-07-05 10:53:12 +02:00
interpret `--` as the end of options, and will simply print this string
if given.
### Options
missed some table formatting in last commit.
2024-10-19 00:57:25 +02:00
Option|Description|
------|-----------|
|`-n`|The trailing newline is suppressed.|
|`-e`|Interpretation of the following backslash-escaped characters (below) is enabled.|
|`-E`|Disables the interpretation of these escape characters, even on systems where they are interpreted by default.|
Convert all builtin commands to Markdown
2023-07-05 10:53:12 +02:00
### Escape sequences
missed some table formatting in last commit.
2024-10-19 00:57:25 +02:00
|Escape|Description|
|------|-----------|
|`\a`|alert (bell)|
|`\b`|backspace|
|`\c`|suppress further output|
|`\e`|
|`\E`|an escape character|
|`\f`|form feed|
|`\n`|new line|
|`\r`|carriage return|
|`\t`|horizontal tab|
|`\v`|vertical tab|
|`\\`|backslash|
|`\0nnn`|the eight-bit character whose value is the octal value nnn (zero to three octal digits)|
|`\xHH`|the eight-bit character whose value is the hexadecimal value HH (one or two hex digits)|
|`\uHHHH`|the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value HHHH (one to four hex digits)|
|`\UHHHHHHHH`|the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value HHHHHHHH (one to eight hex digits)|
Convert all builtin commands to Markdown
2023-07-05 10:53:12 +02:00
## Examples
## Portability considerations
- `echo` is a portability train wreck. No major shell follows POSIX
completely, and any shell that attempts to do so should be
considered horribly broken.
[SUSv4](http://pubs.opengroup.org/onlinepubs/9699919799/utilities/echo.html#tag_20_37)
specifies that `echo` **shall not** include any options. Further, it
specifies that the behavior of `-n` as a first argument shall be
determined by the implementation, unless XSI is followed, in which
case `-n` is always treated as a string, and backslash escapes are
interpreted by default. `dash` has the misfeature of following this
and interpreting escapes by default, but includes a `-n` feature for
Updated table formatting, call-outs, html comments, improper escapes.
2024-10-08 06:00:17 +02:00
suppressing newlines nevertheless.
In practice, if you're able to assume a korn-like shell including
Convert all builtin commands to Markdown
2023-07-05 10:53:12 +02:00
bash, mksh, or zsh, `echo` when used in simple cases is generally
reliable. For example, in the very common situation in which echo is
supplied with a single argument and whose output is to have a
newline appended, using `echo` is considered common practice.
- **Never use options to `echo`! *Ever*!** Any time you feel tempted
to use `echo -e`, `-n`, or any other special feature of echo, **use
Fix hyperlinks of markdown pages at depth 3 find docs/ -depth 3 -name '*.md' | xargs grep '(.*/' -l | \ xargs -I{} \ sed -i '' \ -e 's%(/\([^/#).][^/#).]*\)/\([^/#).][^/#).]*\)\(.md\)\{0\})%(../../\1/\2.md)%g' \ -e 's%(/\([^/#).][^/#).]*\)/\([^/#).][^/#).]*\)#\([a-zA-Z_-][0-9a-zA-Z_-]*\))%(../../\1/\2.md#\3)%g' \ -e 's%(/\([^/#).][^/#).]*\)/\([^/#).][^/#).]*\)/\([^/#).][^/#).]*\)\(.md\)\{0\})%(../../\1/\2/\3.md)%g' \ -e 's%(/\([^/#).][^/#).]*\)/\([^/#).][^/#).]*\)/\([^/#).][^/#).]*\)#\([a-zA-Z_-][0-9a-zA-Z_-]*\))%(../../\1/\2/\3.md#\4)%g' \ -e 's%](\([^:.>)#][^:.>)#]*\))%](../../\1.md)%g' \ -e 's%](\([^:.>)#][^:.>)#]*\)#\([^:.>)#][^:.>)#]*\))%](../../\1.md#\2)%g' \ {} Related to https://github.com/flokoe/bash-hackers-wiki/issues/10
2024-01-29 02:07:56 +01:00
[printf](../../commands/builtin/printf.md) instead!** If portability is a
Convert all builtin commands to Markdown
2023-07-05 10:53:12 +02:00
requirement, you should consider using `printf` *exclusively* and
just ignore that `echo` even exists. If you must use `echo -e` and
refuse to use `printf`, it is usually acceptable to use \'\'echo
\$\'\...\' \'\'if targeting only shells that support this special
quoting style.
- `ksh93` has a `print` command, which if coding specifically for
`ksh93` should be preferred over `echo`.
Fix hyperlinks of markdown pages at depth 3 find docs/ -depth 3 -name '*.md' | xargs grep '(.*/' -l | \ xargs -I{} \ sed -i '' \ -e 's%(/\([^/#).][^/#).]*\)/\([^/#).][^/#).]*\)\(.md\)\{0\})%(../../\1/\2.md)%g' \ -e 's%(/\([^/#).][^/#).]*\)/\([^/#).][^/#).]*\)#\([a-zA-Z_-][0-9a-zA-Z_-]*\))%(../../\1/\2.md#\3)%g' \ -e 's%(/\([^/#).][^/#).]*\)/\([^/#).][^/#).]*\)/\([^/#).][^/#).]*\)\(.md\)\{0\})%(../../\1/\2/\3.md)%g' \ -e 's%(/\([^/#).][^/#).]*\)/\([^/#).][^/#).]*\)/\([^/#).][^/#).]*\)#\([a-zA-Z_-][0-9a-zA-Z_-]*\))%(../../\1/\2/\3.md#\4)%g' \ -e 's%](\([^:.>)#][^:.>)#]*\))%](../../\1.md)%g' \ -e 's%](\([^:.>)#][^:.>)#]*\)#\([^:.>)#][^:.>)#]*\))%](../../\1.md#\2)%g' \ {} Related to https://github.com/flokoe/bash-hackers-wiki/issues/10
2024-01-29 02:07:56 +01:00
[printf](../../commands/builtin/printf.md) still includes most of the
Convert all builtin commands to Markdown
2023-07-05 10:53:12 +02:00
functionality of both, and should usually be the most preferred
option.
## See also
Fix hyperlinks of markdown pages at depth 3 find docs/ -depth 3 -name '*.md' | xargs grep '(.*/' -l | \ xargs -I{} \ sed -i '' \ -e 's%(/\([^/#).][^/#).]*\)/\([^/#).][^/#).]*\)\(.md\)\{0\})%(../../\1/\2.md)%g' \ -e 's%(/\([^/#).][^/#).]*\)/\([^/#).][^/#).]*\)#\([a-zA-Z_-][0-9a-zA-Z_-]*\))%(../../\1/\2.md#\3)%g' \ -e 's%(/\([^/#).][^/#).]*\)/\([^/#).][^/#).]*\)/\([^/#).][^/#).]*\)\(.md\)\{0\})%(../../\1/\2/\3.md)%g' \ -e 's%(/\([^/#).][^/#).]*\)/\([^/#).][^/#).]*\)/\([^/#).][^/#).]*\)#\([a-zA-Z_-][0-9a-zA-Z_-]*\))%(../../\1/\2/\3.md#\4)%g' \ -e 's%](\([^:.>)#][^:.>)#]*\))%](../../\1.md)%g' \ -e 's%](\([^:.>)#][^:.>)#]*\)#\([^:.>)#][^:.>)#]*\))%](../../\1.md#\2)%g' \ {} Related to https://github.com/flokoe/bash-hackers-wiki/issues/10
2024-01-29 02:07:56 +01:00
- [printf](../../commands/builtin/printf.md)
Convert all builtin commands to Markdown
2023-07-05 10:53:12 +02:00
- <http://cfajohnson.com/shell/cus-faq.html#Q0b>
- <http://www.in-ulm.de/~mascheck/various/echo+printf/>
Reference in New Issue Copy Permalink