Difference between revisions of "Core utilities"

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m (Style, shred note added)
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== grep ==
 
== grep ==
  
[[Wikipedia:grep|grep]] is a command line text search utility originally written for Unix. The '''grep''' command searches files or standard input globally for lines matching a given regular expression, and prints them to the program's standard output.
+
[[Wikipedia:grep|grep]] is a command line text search utility originally written for Unix. The '''grep''' command searches files or standard input globally for lines matching a given regular expression, and prints them to the program's standard output. Beyond aesthetics, '''grep''''s color output is immensely useful for learning '''regexp''' and '''grep''''s functionality.
  
Beyond aesthetics, '''grep''''s color output is immensely useful for learning '''regexp''' and '''grep''''s functionality.
+
To use the default colors for '''grep''', write the following entry to your shell configuration file, e.g. if using [[Bash]]:
 
+
{{hc|~/.bashrc|2=alias grep='grep --color=auto'}}
To use the default colors for grep, write the following entry to {{ic|~/.bashrc}}:
+
alias grep='grep --color=auto'  
+
 
Alternatively, you can set the '''GREP_OPTIONS''' [[Environment Variables|environment variable]] [http://www.gnu.org/software/grep/manual/html_node/Environment-Variables.html] bearing in mind this may break some scripts that use '''grep''' [http://brainstorm.ubuntu.com/idea/24141/]:  
 
Alternatively, you can set the '''GREP_OPTIONS''' [[Environment Variables|environment variable]] [http://www.gnu.org/software/grep/manual/html_node/Environment-Variables.html] bearing in mind this may break some scripts that use '''grep''' [http://brainstorm.ubuntu.com/idea/24141/]:  
 
  export GREP_OPTIONS='--color=auto'
 
  export GREP_OPTIONS='--color=auto'
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=== Colored output through environment variables ===
 
=== Colored output through environment variables ===
  
Add the following lines to your shell configuration file, e.g. {{ic|~/.bashrc}} if using [[Bash]]:
+
Add the following lines to your shell configuration file:
  
export LESS=-R
+
{{hc|~/.bashrc|2=
export LESS_TERMCAP_me=$(printf '\e[0m')
+
export LESS=-R
export LESS_TERMCAP_se=$(printf '\e[0m')
+
export LESS_TERMCAP_me=$(printf '\e[0m')
export LESS_TERMCAP_ue=$(printf '\e[0m')
+
export LESS_TERMCAP_se=$(printf '\e[0m')
export LESS_TERMCAP_mb=$(printf '\e[1;32m')
+
export LESS_TERMCAP_ue=$(printf '\e[0m')
export LESS_TERMCAP_md=$(printf '\e[1;34m')
+
export LESS_TERMCAP_mb=$(printf '\e[1;32m')
export LESS_TERMCAP_us=$(printf '\e[1;32m')
+
export LESS_TERMCAP_md=$(printf '\e[1;34m')
export LESS_TERMCAP_so=$(printf '\e[1;44;1m')
+
export LESS_TERMCAP_us=$(printf '\e[1;32m')
 +
export LESS_TERMCAP_so=$(printf '\e[1;44;1m')
 +
}}
  
Change values as you like. References: [[Wikipedia:ANSI_escape_code#Colors]].
+
Change values as you like. References: [[Wikipedia:ANSI_escape_code#Colors|ANSI escape code]].
  
 
=== Colored output through wrappers ===
 
=== Colored output through wrappers ===
  
You can enable code syntax coloring in '''less'''. First, install {{Pkg|source-highlight}}, then add these lines to your {{ic|~/.bashrc}}:
+
You can enable code syntax coloring in '''less'''. First, install {{Pkg|source-highlight}}, then add these lines to your shell configuration file:
export LESSOPEN="| /usr/bin/source-highlight-esc.sh %s"
+
{{hc|~/.bashrc|<nowiki>
export LESS='-R '
+
export LESSOPEN="| /usr/bin/source-highlight-esc.sh %s"
 +
export LESS='-R '
 +
</nowiki>}}
  
 
Frequent users of the command line interface might want to install {{Pkg|lesspipe}}.
 
Frequent users of the command line interface might want to install {{Pkg|lesspipe}}.
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Users may now list the compressed files inside of an archive using their pager:
 
Users may now list the compressed files inside of an archive using their pager:
  
{{hc|$ less compressed_file.tar.gz|<nowiki>
+
{{hc|$ less compressed_file.tar.gz|2=
 
==> use tar_file:contained_file to view a file in the archive
 
==> use tar_file:contained_file to view a file in the archive
 
-rw------- username/group  695 2008-01-04 19:24 compressed_file/content1
 
-rw------- username/group  695 2008-01-04 19:24 compressed_file/content1
 
-rw------- username/group  43 2007-11-07 11:17 compressed_file/content2
 
-rw------- username/group  43 2007-11-07 11:17 compressed_file/content2
 
compressed_file.tar.gz (END)
 
compressed_file.tar.gz (END)
</nowiki>}}
+
}}
  
 
'''lesspipe''' also grants '''less''' the ability of interfacing with files other than archives, serving as an alternative for the specific command associated for that file-type (such as viewing HTML via {{Pkg|html2text}}).
 
'''lesspipe''' also grants '''less''' the ability of interfacing with files other than archives, serving as an alternative for the specific command associated for that file-type (such as viewing HTML via {{Pkg|html2text}}).
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=== Vim as alternative pager ===
 
=== Vim as alternative pager ===
  
'''Vim''' has a script to view the content of text files, compressed files, binaries, directories. Add the following line to your shell configuration file, e.g. {{ic|~/.bashrc}} for Bash:
+
'''Vim''' has a script to view the content of text files, compressed files, binaries, directories. Add the following line to your shell configuration file:
alias less='/usr/share/vim/vim73/macros/less.sh'
+
{{hc|~/.bashrc|2=alias less='/usr/share/vim/vim73/macros/less.sh'}}
  
 
== ls ==
 
== ls ==
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  alias ls='ls --color=auto'
 
  alias ls='ls --color=auto'
  
The next step will further enhance the colored '''ls''' output; for example, broken (orphan) symlinks will start showing in a red hue. Add the following to {{ic|~/.bashrc}} and relogin, or source the file:
+
The next step will further enhance the colored '''ls''' output; for example, broken (orphan) symlinks will start showing in a red hue. Add the following to your shell configuration file:
eval $(dircolors -b)
+
{{hc|~/.bashrc|eval $(dircolors -b)}}
  
 
== rm ==
 
== rm ==
Line 89: Line 91:
 
  alias rm=' timeout 3 rm -Iv'
 
  alias rm=' timeout 3 rm -Iv'
 
This alias suspends '''rm''' after three seconds, asks confirmation to delete three or more files, lists the operations in progress and does not store itself in the shell history file if the shell is configured to ignore space starting commands.
 
This alias suspends '''rm''' after three seconds, asks confirmation to delete three or more files, lists the operations in progress and does not store itself in the shell history file if the shell is configured to ignore space starting commands.
 +
 +
A similar solution may be used for '''shred'''.
  
 
== See also ==
 
== See also ==
  
* [http://www.reddit.com/r/commandline/comments/19garq/a_sampling_of_coreutils_120/ A sampling of coreutils] [http://www.reddit.com/r/commandline/comments/19ge6v/a_sampling_of_coreutils_2040/ , part 2] [http://www.reddit.com/r/commandline/comments/19j1w3/a_sampling_of_coreutils_4060/ , part 3] an overview of commands in coreutils
+
* [http://www.reddit.com/r/commandline/comments/19garq/a_sampling_of_coreutils_120/ A sampling of coreutils] [http://www.reddit.com/r/commandline/comments/19ge6v/a_sampling_of_coreutils_2040/ , part 2] [http://www.reddit.com/r/commandline/comments/19j1w3/a_sampling_of_coreutils_4060/ , part 3] - An overview of commands in coreutils

Revision as of 21:46, 3 June 2013

Summary help replacing me
Tips and tricks related to so-called "core" utilities on a GNU/Linux system.
Related
Commandline Tools
General Recommendations
GNU Project

This article deals with so-called "core" utilities on a GNU/Linux system, such as less, ls, and grep. The scope of this article includes -- but is not limited to -- those utilities included with the GNU coreutils package. What follows are various tips and tricks and other helpful information related to these utilities. If sections grow too detailed, please split into separate articles.

grep

grep is a command line text search utility originally written for Unix. The grep command searches files or standard input globally for lines matching a given regular expression, and prints them to the program's standard output. Beyond aesthetics, grep's color output is immensely useful for learning regexp and grep's functionality.

To use the default colors for grep, write the following entry to your shell configuration file, e.g. if using Bash:

~/.bashrc
alias grep='grep --color=auto'

Alternatively, you can set the GREP_OPTIONS environment variable [1] bearing in mind this may break some scripts that use grep [2]:

export GREP_OPTIONS='--color=auto'

To include file line numbers in the output, add "-n":

alias grep='grep -n --color=auto' 

The environment variable GREP_COLORS may be used to specify different colors than the defaults.

less

less is a terminal pager program used to view the contents of a text file one screen at a time. Whilst similar to other pages such as more and pg, less offers a more advanced interface and complete feature-set.[3]

Colored output through environment variables

Add the following lines to your shell configuration file:

~/.bashrc
export LESS=-R
export LESS_TERMCAP_me=$(printf '\e[0m')
export LESS_TERMCAP_se=$(printf '\e[0m')
export LESS_TERMCAP_ue=$(printf '\e[0m')
export LESS_TERMCAP_mb=$(printf '\e[1;32m')
export LESS_TERMCAP_md=$(printf '\e[1;34m')
export LESS_TERMCAP_us=$(printf '\e[1;32m')
export LESS_TERMCAP_so=$(printf '\e[1;44;1m')

Change values as you like. References: ANSI escape code.

Colored output through wrappers

You can enable code syntax coloring in less. First, install source-highlight, then add these lines to your shell configuration file:

~/.bashrc
export LESSOPEN="| /usr/bin/source-highlight-esc.sh %s"
export LESS='-R '

Frequent users of the command line interface might want to install lesspipe.

Users may now list the compressed files inside of an archive using their pager:

$ less compressed_file.tar.gz
==> use tar_file:contained_file to view a file in the archive
-rw------- username/group  695 2008-01-04 19:24 compressed_file/content1
-rw------- username/group   43 2007-11-07 11:17 compressed_file/content2
compressed_file.tar.gz (END)

lesspipe also grants less the ability of interfacing with files other than archives, serving as an alternative for the specific command associated for that file-type (such as viewing HTML via html2text).

Re-login after installing lesspipe in order to activate it, or source /etc/profile.d/lesspipe.sh.

Vim as alternative pager

Vim has a script to view the content of text files, compressed files, binaries, directories. Add the following line to your shell configuration file:

~/.bashrc
alias less='/usr/share/vim/vim73/macros/less.sh'

ls

ls is a command to list files in Unix and Unix-like operating systems.

Colored output can be enabled with a simple alias. File ~/.bashrc should already have the following entry copied from /etc/skel/.bashrc:

alias ls='ls --color=auto'

The next step will further enhance the colored ls output; for example, broken (orphan) symlinks will start showing in a red hue. Add the following to your shell configuration file:

~/.bashrc
eval $(dircolors -b)

rm

rm is a command to delete files and directories. It could be very dangerous so it is prudent to limit its scope:

alias rm=' timeout 3 rm -Iv'

This alias suspends rm after three seconds, asks confirmation to delete three or more files, lists the operations in progress and does not store itself in the shell history file if the shell is configured to ignore space starting commands.

A similar solution may be used for shred.

See also