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[[Category:System administration]]
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[[Category:Command-line]]
[[Category:Command shells]]
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[[Category:Lists of software]]
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{{Related articles start}}
 
{{Related articles start}}
{{Related|Bash}}
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{{Related|Command-line shell}}
{{Related|Zsh}}
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{{Related|Users and groups}}
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{{Related|systemd}}
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{{Related|pacman}}
 
{{Related|General recommendations}}
 
{{Related|General recommendations}}
{{Related|GNU Project}}
 
{{Related|sudo}}
 
{{Related|cron}}
 
{{Related|File system search}}
 
{{Related|man page}}
 
{{Related|Securely wipe disk#shred}}
 
{{Related|File permissions and attributes}}
 
 
{{Related articles end}}
 
{{Related articles end}}
  
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 {{Pkg|coreutils}} package. What follows are various tips and tricks and other helpful information related to these utilities.
+
''Core utilities'' are the basic, fundamental tools of a [[GNU]]/[[Linux]] system. On Arch Linux they are found in the [[base group]]. This article provides an incomplete overview of them, links their documentation and describes useful alternatives. The scope of this article includes, but is not limited to, the [https://www.gnu.org/software/coreutils/coreutils.html GNU coreutils]. Most core utilities are traditional [[Wikipedia:Unix|Unix]] tools (see [[Heirloom]]) and many were standardized by [[Wikipedia:POSIX|POSIX]] but have been developed further to provide more features.
  
== Basic commands ==
+
Most command-line interfaces are documented in [[man page]]s, utilities by the [[GNU Project]] are documented primarily in [[Info manual]]s, some [[shell]]s provide a {{ic|help}} command for shell builtin commands. Additionally most utilities print their usage when run with the {{ic|--help}} flag.
  
The following table lists basic shell commands every Linux user should be familiar with. Commands in '''bold''' are part of the shell, others are separate programs called from the shell. See the below sections and ''Related articles'' for details.
+
== Essentials ==
  
{| class="wikitable"
+
The following table lists some important utilities which Arch Linux users should be familiar with. See also {{man|1|intro}}.
! Command
+
 
! Description
+
{| class=wikitable
! Example
+
! Package !! Utility !! Description !! Documentation !! Alternatives
 +
|-
 +
| shell built-ins || cd || change directory || {{man|1p|cd}}
 +
|-
 +
|rowspan=12| GNU {{Pkg|coreutils}}
 +
| ls || list directory || {{man|1|ls}}, [https://www.gnu.org/software/coreutils/manual/html_node/ls-invocation.html info] || {{Pkg|exa}}, {{Pkg|lsd}}, {{Pkg|tree}}
 +
|-
 +
| cat || concatenate files to stdout || {{man|1|cat}}, [https://www.gnu.org/software/coreutils/manual/html_node/cat-invocation.html info] || {{man|1|tac}}, {{Pkg|bat}}
 +
|-
 +
| mkdir || make directory || {{man|1|mkdir}}, [https://www.gnu.org/software/coreutils/manual/html_node/mkdir-invocation.html info]
 +
|-
 +
| rmdir || remove empty directory || {{man|1|rmdir}}, [https://www.gnu.org/software/coreutils/manual/html_node/rmdir-invocation.html info]
 +
|-
 +
| rm || remove files or directories || {{man|1|rm}}, [https://www.gnu.org/software/coreutils/manual/html_node/rm-invocation.html info] || [[shred]]
 
|-
 
|-
| man
+
| cp || copy files or directories || {{man|1|cp}}, [https://www.gnu.org/software/coreutils/manual/html_node/cp-invocation.html info]
| Show manual page for a command
 
| man ed
 
 
|-
 
|-
| '''cd'''
+
| mv || move files or directories || {{man|1|mv}}, [https://www.gnu.org/software/coreutils/manual/html_node/mv-invocation.html info]
| Change directory
 
| cd /etc/pacman.d
 
 
|-
 
|-
| mkdir
+
| ln || make hard or symbolic links || {{man|1|ln}}, [https://www.gnu.org/software/coreutils/manual/html_node/ln-invocation.html info]
| Create a directory
 
| mkdir ~/newfolder
 
 
|-
 
|-
| rmdir
+
| [[chown]] || change file owner and group || {{man|1|chown}}, [https://www.gnu.org/software/coreutils/manual/html_node/chown-invocation.html info] || {{man|1|chgrp}}
| Remove empty directory
 
| rmdir ~/emptyfolder
 
 
|-
 
|-
| rm
+
| [[chmod]] || change file permissions || {{man|1|chmod}}, [https://www.gnu.org/software/coreutils/manual/html_node/chmod-invocation.html info]
| Remove a file
 
| rm ~/file.txt
 
 
|-
 
|-
| rm -r
+
| [[dd]] || convert and copy a file || {{man|1|dd}}, [https://www.gnu.org/software/coreutils/manual/html_node/dd-invocation.html info]
| Remove directory and contents
 
| rm -r ~/.cache
 
 
|-
 
|-
| ls
+
| df || report file system disk space usage || {{man|1|df}}, [https://www.gnu.org/software/coreutils/manual/html_node/df-invocation.html info]
| List files
 
| ls *.avi
 
 
|-
 
|-
| ls -a
+
| GNU {{Pkg|tar}} || [[tar]] || tar archiver || {{man|1|tar}}, [https://www.gnu.org/software/tar/manual/html_chapter/index.html info] || [[archiver]]s
| List hidden files
 
| ls -a /home/archie
 
 
|-
 
|-
| ls -al
+
| GNU {{Pkg|less}} || less || terminal pager || {{man|1|less}} || [[terminal pager]]s
| List hidden files and file properties
 
|
 
 
|-
 
|-
| mv
+
| GNU {{Pkg|findutils}} || find || search files or directories || {{man|1|find}}, [https://www.gnu.org/software/findutils/manual/html_node/find_html/index.html info], [[GregsWiki:UsingFind|GregsWiki]] || [[#find alternatives]]
| Move a file
 
| mv ~/compressed.zip ~/archive/compressed2.zip
 
 
|-
 
|-
| cp
+
| GNU {{Pkg|diffutils}} || diff || compare files line by line || {{man|1|diff}}, [https://www.gnu.org/software/diffutils/manual/html_node/Invoking-diff.html info] || [[#diff alternatives]]
| Copy a file
 
| cp ~/.bashrc ~/.bashrc.bak
 
 
|-
 
|-
| chmod +x
+
| GNU {{Pkg|grep}} || grep || print lines matching a pattern || {{man|1|grep}}, [https://www.gnu.org/software/grep/manual/html_node/index.html info] || [[#grep alternatives]]
| Make a file executable
 
| chmod +x ~/.local/bin/myscript.sh
 
 
|-
 
|-
| cat
+
| GNU {{Pkg|sed}} || sed || stream editor || {{man|1|sed}}, [https://www.gnu.org/software/sed/manual/html_node/index.html info], [http://sed.sourceforge.net/sed1line.txt one-liners]
| Show file contents
 
| cat /etc/hostname
 
 
|-
 
|-
| strings
+
| GNU {{Pkg|gawk}} || awk || pattern scanning and processing language || {{man|1|gawk}}, [https://www.gnu.org/software/gawk/manual/html_node/index.html info] || {{Pkg|nawk}}, {{AUR|mawk}}
| Show printable characters in binary files
 
| strings /usr/bin/free
 
 
|-
 
|-
| find
+
|rowspan=6| {{Pkg|util-linux}}
| Search for a file
+
| [[Wikipedia:dmesg|dmesg]] || print or control the kernel ring buffer || {{man|1|dmesg}} || [[systemd journal]]
| find ~ -name myfile
 
 
|-
 
|-
| mount
+
| [[lsblk]] || list block devices || {{man|8|lsblk}}
| Mount a partition
 
| mount /dev/sdc1 /media/usb
 
 
|-
 
|-
| df -h
+
| [[mount]] || mount a filesystem || {{man|8|mount}}
| Show remaining space on all partitions
 
|
 
 
|-
 
|-
| ps -A
+
| [[umount]] || unmount a filesystem || {{man|8|umount}}
| Show all running processes
 
|
 
 
|-
 
|-
| killall
+
| [[su]] || substitute user || {{man|1|su}} || [[sudo]]
| Kill all running instances of a process
+
|-
|
+
| kill || terminate a process || {{man|1|kill}} || {{man|1|pkill}}, {{man|1|killall}}
 +
|-
 +
|rowspan=3| {{Pkg|procps-ng}}
 +
| pgrep || look up processes by name or attributes || {{man|1|pgrep}} || {{man|1|pidof}}
 +
|-
 +
| ps || show information about processes || {{man|1|ps}} ||rowspan=2| {{man|1|top}}, {{Pkg|htop}}
 +
|-
 +
| free || display amount of free and used memory || {{man|1|free}}
 
|}
 
|}
  
== cat ==
+
=== Preventing data loss ===
 
 
[[Wikipedia:cat_(Unix)|cat]] (''catenate'') is a standard Unix utility that concatenates and lists files.
 
 
 
* Because ''cat'' is not a built-in shell, on many occasions you may find it more convenient to use a [[Wikipedia:Redirection (computing)|redirection]], for example in scripts, or if you care a lot about performance. In fact {{ic|< ''file''}} does the same as {{ic|cat ''file''}}.
 
 
 
* ''cat'' is able to work with multiple lines, although this is sometimes regarded as bad practice:
 
 
 
{{bc|
 
$ cat << EOF >> ''path/file''
 
''first line''
 
...
 
''last line''
 
EOF
 
}}
 
: A better alternative is the ''echo'' command:
 
{{bc|
 
$ echo "\
 
''first line''
 
...
 
''last line''" \
 
>> ''path/file''
 
}}
 
 
 
* If you need to list file lines in reverse order, there is a utility called [[Wikipedia:tac (Unix)|tac]] (''cat'' reversed).
 
 
 
== dd ==
 
 
 
[[Wikipedia:dd (Unix)|dd]] is a command on Unix and Unix-like operating systems whose primary purpose is to convert and copy a file.
 
 
 
{{Note|''cp'' does the same as ''dd'' without any operands but is not designed for more versatile disk wiping procedures.}}
 
 
 
=== Checking progress of dd while running ===
 
 
 
By default, there is no output of ''dd'' until the task has finished. With ''kill'' and the {{ic|USR1}} signal you can force status output without actually killing the program. Open up a second root terminal and issue the following command:
 
# killall -USR1 dd
 
 
 
{{Note|This will affect all other running ''dd'' processes as well.}}
 
 
 
Or:
 
# kill -USR1 ''pid_of_dd_command''
 
 
 
For example:
 
# kill -USR1 $(pidof dd)
 
 
 
This causes ''dd'' to output immediate progress into the terminal. For example:
 
605+0 records in
 
605+0 records out
 
634388480 bytes (634 MB) copied, 8.17097 s, 77.6 MB/s
 
 
 
==== Using pipe viewer ====
 
 
 
As an alternative you can use {{Pkg|pv}} to monitor the dd-pipeline:
 
# dd if=''/source/filestream'' | pv -''monitor_options'' -s ''size_of_file'' | dd of=''/destination/filestream''
 
 
 
To use the pipe viewer more easily you can add this to your bashrc or zshrc:
 
copy() {
 
    size=$(stat -c%s $1)
 
    dd if=$1 &> /dev/null | pv -petrb -s $size | dd of=$2
 
}
 
 
 
And use it with:
 
# copy ''/source/file'' ''/destination/file''
 
 
 
=== dd spin-offs ===
 
 
 
{{Move|Disk cloning|See [[Talk:Disk_cloning#ddrescue]].}}
 
 
 
Other ''dd''-like programs feature periodical status output, e.g. a simple progress bar.
 
 
 
; dcfldd : {{Pkg|dcfldd}} is an enhanced version of dd with features useful for forensics and security. It accepts most of dd's parameters and includes status output. The last stable version of dcfldd was released on December 19, 2006.<sup>[http://dcfldd.sourceforge.net/]</sup>
 
 
 
; ddrescue : GNU {{Pkg|ddrescue}} is a data recovery tool. It is capable of ignoring read errors, which is a useless feature for disk wiping in almost any case. See the [http://www.gnu.org/software/ddrescue/manual/ddrescue_manual.html official manual] for details.
 
 
 
== grep ==
 
 
 
[[Wikipedia:grep|grep]] (from [[Wikipedia:ed|ed]]'s ''g/re/p'', ''global/regular expression/print'') 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.
 
 
 
* Remember that ''grep'' handles files, so a construct like {{ic|cat ''file'' <nowiki>|</nowiki> grep ''pattern''}} is replaceable with {{ic|grep ''pattern'' ''file''}}
 
 
 
* ''grep'' alternatives optimized for VCS source code do exist, such as {{Pkg|the_silver_searcher}} and {{Pkg|ack}}.
 
 
 
=== Colored output ===
 
 
 
{{ic|grep}}'s color output can be helpful for learning [[Wikipedia:regexp|regexp]] and additional {{ic|grep}} functionality.
 
 
 
To enable ''grep'' coloring write the following entry to the shell configuration file (e.g. if using [[Bash]]):
 
 
 
{{hc|~/.bashrc|2=alias grep='grep --color=auto'}}
 
 
 
To include file line numbers in the output, add the option {{ic|-n}} to the line.
 
 
 
The environment variable {{ic|GREP_COLOR}} can be used to define the default highlight color (the default is red).  To change the color find the [http://www.tldp.org/HOWTO/Bash-Prompt-HOWTO/x329.html ANSI escape sequence] for the color liked and add it:
 
 
 
export GREP_COLOR="1;32"
 
 
 
{{ic|GREP_COLORS}} may be used to define specific searches.
 
 
 
=== Standard error ===
 
 
 
Some commands send their output to standard error, and grep has no apparent effect. In this case, redirect standard error next to standard out:
 
 
 
$ ''command'' 2>&1 | grep ''args''
 
 
 
or Bash 4 shorthand:
 
 
 
$ ''command'' |& grep ''args''
 
 
 
See also [http://www.tldp.org/LDP/abs/html/io-redirection.html I/O Redirection].
 
 
 
== find ==
 
 
 
''find'' is part of the {{Pkg|findutils}} package, which belongs to the {{Grp|base}} package group.
 
 
 
One would probably expect a ''find'' command to take as argument a file name and search the filesystem for files matching that name. For a program that does exactly that see [[#locate]] below.
 
 
 
Instead, find takes a set of directories and matches each file under them against a set of expressions. This design allows for some very powerful "one-liners" that would not be possible using the "intuitive" design described above. See [http://mywiki.wooledge.org/UsingFind UsingFind] for usage details.
 
 
 
== locate ==
 
 
 
{{ic|locate}} is a common Unix tool for quickly finding files by name. It offers speed improvements over the [http://en.wikipedia.org/wiki/Find find] tool by searching a pre-constructed database file, rather than the filesystem directly. The downside of this approach is that changes made since the construction of the database file cannot be detected by {{ic|locate}}. This problem is minimised by regular, typically scheduled use of the {{ic|updatedb}} command, which (as the name suggests) updates the database.
 
 
 
{{Note|Although in other distros {{ic|locate}} and {{ic|updatedb}} are in the {{Pkg|findutils}} package, they are no longer present in Arch's package. To use it, install the {{Pkg|mlocate}} package. mlocate is a newer implementation of the tool, but is used in exactly the same way.}}
 
 
 
Before {{ic|locate}} can be used, the database will need to be created. To do this, simply run {{ic|updatedb}} as root.
 
 
 
See also [http://jvns.ca/blog/2015/03/05/how-the-locate-command-works-and-lets-rewrite-it-in-one-minute/ How locate works and rewrite it in one minute]
 
 
 
=== Keeping the database up-to-date ===
 
 
 
When {{ic|mlocate}} is installed, a script is automatically scheduled to run daily via {{ic|systemd}}, to update the database. You can also manually run {{ic|updatedb}} as root at any time.
 
 
 
To save time, the {{ic|updatedb}} can be (and by default is) configured to ignore certain filesystems and paths by editing {{ic|/etc/updatedb.conf}}. {{ic|man updatedb.conf}} will tell you about the semantics of this file. It is worth noting that among the paths ignored in the default configuration (i.e. those in the "PRUNEPATHS" string) are {{ic|/media}} and {{ic|/mnt}}, so {{ic|locate}} may not discover files on external devices.
 
 
 
== iconv ==
 
 
 
{{ic|iconv}} converts the encoding of characters from one codeset to another.
 
  
The following command will convert the file {{ic|foo}} from ISO-8859-15 to UTF-8 saving it to {{ic|foo.utf}}:
+
{{ic|rm}}, {{ic|mv}}, {{ic|cp}} and shell redirections happily delete or overwrite files without asking. {{ic|rm}}, {{ic|mv}}, and {{ic|cp}} all support the {{ic|-i}} flag to prompt the user before every removal / overwrite. Some users like to enable the {{ic|-i}} flag by default using [[alias]]es. Relying upon these shell options can be dangerous, because you get used to them, resulting in potential data loss when you use another system or user that does not have them. The best way to prevent data loss is to create [[backup]]s.
  
$ iconv -f ISO-8859-15 -t UTF-8 foo >foo.utf
+
== Nonessentials ==
  
See {{ic|man iconv}} for more details.
+
This table lists core utilities that often come in handy.
  
=== Convert a file in place ===
+
{| class=wikitable
{{Tip|You can use {{pkg|recode}} instead of iconv if you do not want to touch the mtime.}}
+
! Package !! Utility !! Description !! Documentation !! Alternatives
Unlike [[#sed|sed]], ''iconv'' does not provide an option to convert a file in place. However, {{ic|sponge}} can be used to handle it, it comes with {{pkg|moreutils}}.
 
 
 
$ iconv -f WINDOWS-1251 -t UTF-8 foobar.txt | sponge foobar.txt
 
 
 
See {{ic|man sponge}} for details.
 
 
 
== ip ==
 
 
 
[[Wikipedia:Iproute2|ip]] allows you to show information about network devices, IP addresses, routing tables, and other objects in the Linux [[Wikipedia:Internet Protocol|IP]] software stack. By appending various commands, you can also manipulate or configure most of these objects.
 
 
 
{{Note|The ''ip'' utility is provided by the {{Pkg|iproute2}} package, which is included in the {{Grp|base}} group.}}
 
 
 
{| class="wikitable"
 
! Object !! Purpose !! Manual Page Name
 
 
|-
 
|-
| ip addr || protocol address management || ip-address
+
|rowspan=3| shell built-ins
 +
| alias || define or display aliases || {{man|1p|alias}}
 
|-
 
|-
| ip addrlabel || protocol address label management || ip-addrlabel
+
| type || print the type of a command || {{man|1p|type}} || {{man|1|which}}
 
|-
 
|-
| ip l2tp || tunnel Ethernet over IP (L2TPv3) || ip-l2tp
+
| time || time a command || {{man|1p|time}}
 
|-
 
|-
| ip link || network device configuration || ip-link
+
|rowspan=11| GNU {{Pkg|coreutils}}
 +
| tee || read stdin and write to stdout and files || {{man|1|tee}}, [https://www.gnu.org/software/coreutils/manual/html_node/tee-invocation.html info]
 
|-
 
|-
| ip maddr || multicast addresses management || ip-maddress
+
| mktemp || make a temporary file or directory || {{man|1|mktemp}}, [https://www.gnu.org/software/coreutils/manual/html_node/mktemp-invocation.html info]
 
|-
 
|-
| ip monitor || watch for netlink messages || ip-monitor
+
| cut || print selected parts of lines || {{man|1|cut}}, [https://www.gnu.org/software/coreutils/manual/html_node/cut-invocation.html info]
 
|-
 
|-
| ip mroute || multicast routing cache management || ip-mroute
+
| tr || translate or delete characters || {{man|1|tr}}, [https://www.gnu.org/software/coreutils/manual/html_node/tr-invocation.html info]
 
|-
 
|-
| ip mrule || rule in multicast routing policy db ||
+
| od || dump files in octal and other formats || {{man|1|od}}, [https://www.gnu.org/software/coreutils/manual/html_node/od-invocation.html info] || {{man|1|hexdump}}, [[vim]]'s {{man|1|xxd}}
 
|-
 
|-
| ip neigh || neighbour/ARP tables management || ip-neighbour
+
| sort || sort lines || {{man|1|sort}}, [https://www.gnu.org/software/coreutils/manual/html_node/sort-invocation.html info]
 
|-
 
|-
| ip netns || process network namespace management || ip-netns
+
| uniq || report or omit repeated lines || {{man|1|uniq}}, [https://www.gnu.org/software/coreutils/manual/html_node/uniq-invocation.html info]
 
|-
 
|-
| ip ntable || neighbour table configuration || ip-ntable
+
| comm || compare two sorted files line by line || {{man|1|comm}}, [https://www.gnu.org/software/coreutils/manual/html_node/comm-invocation.html info]
 
|-
 
|-
| ip route || routing table management || ip-route
+
| head || output the first part of files || {{man|1|head}}, [https://www.gnu.org/software/coreutils/manual/html_node/head-invocation.html info]
 
|-
 
|-
| ip rule || routing policy database management || ip-rule
+
| tail || output the last part of files, or follow files || {{man|1|tail}}, [https://www.gnu.org/software/coreutils/manual/html_node/tail-invocation.html info]
 
|-
 
|-
| ip tcp_metrics || management for TCP Metrics || ip-tcp_metrics
+
| wc || print newline, word and byte count || {{man|1|wc}}, [https://www.gnu.org/software/coreutils/manual/html_node/wc-invocation.html info]
 
|-
 
|-
| ip tunnel || tunnel configuration || ip-tunnel
+
| GNU {{Pkg|binutils}} || strings || print printable characters in binary files || {{man|1|strings}}, [https://sourceware.org/binutils/docs/binutils/strings.html info]
 
|-
 
|-
| ip tuntap || manage TUN/TAP devices ||
+
| GNU {{Pkg|glibc}} || iconv || convert character encodings || {{man|1|iconv}} || {{Pkg|recode}}
 
|-
 
|-
| ip xfrm || manage IPsec policies || ip-xfrm
+
| {{Pkg|file}} || file || guess file type || {{man|1|file}}
 
|}
 
|}
  
The {{ic|help}} command is available for all objects. For example, typing {{ic|ip addr help}} will show you the command syntax available for the address object. For advanced usage see the [http://www.policyrouting.org/iproute2.doc.html iproute2 documentation].
+
The {{Pkg|moreutils}} package provides useful tools like {{man|1|sponge}} that are missing from the GNU coreutils.
 
 
The [[Network configuration]] article shows how the ''ip'' command is used in practice for various common tasks.
 
 
 
{{Note|You might be familiar with the [[Wikipedia:ifconfig|ifconfig]] command, which was used in older versions of Linux for interface configuration. It is now deprecated in Arch Linux; you should use ''ip'' instead. }}
 
 
 
== less ==
 
 
 
[[Wikipedia:less (Unix)|less]] is a terminal pager program used to view the contents of a text file one screen at a time. Whilst similar to other pagers such as [[Wikipedia:more (command)|more]] and [[Wikipedia:pg (Unix)|pg]], ''less'' offers a more advanced interface and complete [http://www.greenwoodsoftware.com/less/faq.html feature-set].
 
 
 
See [[List of applications#Terminal pagers]] for alternatives.
 
 
 
=== Colored output through environment variables ===
 
 
 
Add the following lines to your shell configuration file:
 
 
 
{{hc|~/.bashrc|2=
 
export LESS=-R
 
export LESS_TERMCAP_mb=$'\E[1;31m'
 
export LESS_TERMCAP_md=$'\E[1;36m'
 
export LESS_TERMCAP_me=$'\E[0m'
 
export LESS_TERMCAP_se=$'\E[0m'
 
export LESS_TERMCAP_so=$'\E[01;44;33m'
 
export LESS_TERMCAP_ue=$'\E[0m'
 
export LESS_TERMCAP_us=$'\E[1;32m'
 
}}
 
 
 
Change the values ([[Wikipedia:ANSI escape code#Colors|ANSI escape code]]) as you like.
 
  
{{note|The {{ic|LESS_TERMCAL_''xx''}} variables is currently undocumented in less(1), for a detailed explanation on these sequences, see this [http://unix.stackexchange.com/questions/108699/documentation-on-less-termcap-variables/108840#108840 anwser].}}
+
== Alternatives ==
  
=== Colored output through wrappers ===
+
Alternatives to the core utilities in the {{Grp|base}} group are [[BusyBox]], the [[Heirloom|Heirloom Toolchest]], {{Pkg|9base}}, {{AUR|sbase-git}} and {{AUR|ubase-git}}.
  
You can enable code syntax coloring in ''less''. First, [[install]] {{Pkg|source-highlight}}, then add these lines to your shell configuration file:
+
=== cp alternatives ===
{{hc|~/.bashrc|<nowiki>
 
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}}.
+
Using [[rsync#As cp/mv alternative]] allows you to resume a failed transfer, to show the transfer status, to skip already existing files and to make sure of the destination files integrity using checksums.
  
Users may now list the compressed files inside of an archive using their pager:
+
=== find alternatives ===
  
{{hc|$ less ''compressed_file''.tar.gz|2=
+
* {{App|fd|Simple, fast and user-friendly alternative to find. Ignores hidden and {{ic|.gitignore}}'d files by default.|https://github.com/sharkdp/fd|{{Pkg|fd}}}}
==> use tar_file:contained_file to view a file in the archive
+
* {{App|fuzzy-find|Fuzzy completion for finding files.|https://github.com/silentbicycle/ff|{{AUR|ff-git}}}}
-rw------- ''username''/''group''  695 2008-01-04 19:24 ''compressed_file''/''content1''
+
* {{App|[[mlocate]]|Merging locate/updatedb implementation.|https://pagure.io/mlocate|{{Pkg|mlocate}}}}
-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 {{Pkg|python-html2text}}).
+
For graphical file searchers, see [[List of applications/Utilities#File searching]].
  
Re-login after installing ''lesspipe'' in order to activate it, or source {{ic|/etc/profile.d/lesspipe.sh}}.
+
=== diff alternatives ===
  
=== Vim as alternative pager ===
+
While {{Pkg|diffutils}} does not provide a word-wise diff, several other programs do:
  
[[Vim]] (''visual editor improved'') has a script to view the content of text files, compressed files, binaries, directories. Add the following line to your shell configuration file to use it as a pager:
+
* [[git]] diff can do a word diff with {{ic|--color-words}}, using {{ic|--no-index}} it can also be used for files outside of Git working trees.
{{hc|~/.bashrc|2=alias less='/usr/share/vim/vim74/macros/less.sh'}}
+
* {{App|dwdiff|A word diff front-end for the diff program; supports colors.|https://os.ghalkes.nl/dwdiff.html|{{Pkg|dwdiff}}}}
 +
* {{App|GNU wdiff|A wordwise implementation of GNU diff; does not support colors.|https://www.gnu.org/software/wdiff/|{{Pkg|wdiff}}}}
 +
* {{App|cwdiff|A GNU wdiff wrapper that colorizes the output.|https://github.com/junghans/cwdiff|{{AUR|cwdiff}}, {{AUR|cwdiff-git}}}}
 +
* {{App|icdiff|A colorized diff tool written in Python. "Improved color diff" is meant to supplement normal diff use.|https://github.com/jeffkaufman/icdiff|{{AUR|icdiff}},{{AUR|icdiff-git}}}}
  
There is also an alternative to ''less.sh'' macro, which may work as the {{ic|PAGER}} environment variable. Install {{Pkg|vimpager}} and add the following to your shell configuration file:
+
See also [[List of applications/Utilities#Comparison, diff, merge]].
{{hc|~/.bashrc|2=
 
export PAGER='vimpager'
 
alias less=$PAGER
 
}}
 
  
Now programs that use the {{ic|PAGER}} environment variable, like [[git]], will use ''vim'' as pager.
+
=== grep alternatives ===
  
=== Colored output when reading from stdin ===
+
* {{App|mgrep|A multiline grep.|https://sourceforge.net/projects/multiline-grep/|{{AUR|mgrep}}}}
  
{{Note|It is recommended to add [[#Colored output through environment variables]] to your {{ic|~/.bashrc}} or {{ic|~/.zshrc}}, as the below is based on {{ic|1=export LESS=R}}}}
+
==== Code searchers ====
  
When you run a command and pipe its [[Wikipedia:Standard output|standard output]] (''stdout'') to ''less'' for a paged view (e.g. {{ic|<nowiki>pacman -Qe | less</nowiki>}}), you may find that the output is no longer colored. This is usually because the program tries to detect if its ''stdout'' is an interactive terminal, in which case it prints colored text, and otherwise prints uncolored text. This is good behaviour when you want to redirect ''stdout'' to a file, e.g. {{ic|<nowiki>pacman -Qe > pkglst-backup.txt</nowiki>}}, but less suited when you want to view output in {{ic|less}}.
+
The following three tools aim to replace grep for code search. They do recursive search by default, skip binary files and respect {{ic|.gitignore}}.
  
Some programs provide an option to disable the interactive tty detection:
+
* {{App|ack|A Perl-based grep replacement, aimed at programmers with large trees of heterogeneous source code.|https://beyondgrep.com/|{{Pkg|ack}}}}
 +
* {{App|ripgrep (rg)|A search tool that combines the usability of ag with the raw speed of grep.|https://github.com/BurntSushi/ripgrep|{{Pkg|ripgrep}}}}
 +
* {{App|The Silver Searcher (ag)|Code searching tool similar to Ack, but faster.|https://github.com/ggreer/the_silver_searcher|{{Pkg|the_silver_searcher}}}}
  
# dmesg --color=always | less
+
==== Interactive filters ====
  
In case that the program does not provide any similar option, it is possible to trick the program into thinking its ''stdout'' is an interactive terminal with the following utilities:
+
* {{App|[[fzf]]|General-purpose command-line fuzzy finder, powered by find by default.|https://github.com/junegunn/fzf|{{Pkg|fzf}}, {{AUR|fzf-git}}}}
 
+
* {{App|fzy|A fast, simple fuzzy text selector with an advanced scoring algorithm.|https://github.com/jhawthorn/fzy|{{Pkg|fzy}}, {{AUR|fzy-git}}}}
* {{App|stdoutisatty|A small program which catches the {{ic|isatty}} function call.|https://github.com/lilydjwg/stdoutisatty.|{{AUR|stdoutisatty-git}}}}
+
* {{App|peco|Simplistic interactive filtering tool.|https://github.com/peco/peco|{{AUR|peco}}, {{AUR|peco-git}}}}
:Example: {{ic|stdoutisatty ''program'' <nowiki>| less</nowiki>}}
+
* {{App|percol|Adds flavor of interactive filtering to the traditional pipe concept of the UNIX shell.|https://github.com/mooz/percol|{{Pkg|percol}}, {{AUR|percol-git}}}}
* {{App|unbuffer|A tclsh script comes with expect, it invokes desired program within a pty.|http://expect.sourceforge.net/example/unbuffer.man.html|{{Pkg|expect}}}}
 
:Example: {{ic|unbuffer ''program'' <nowiki>| less</nowiki>}}
 
 
 
Alternatively, using [http://zsh.sourceforge.net/Doc/Release/Zsh-Modules.html#The-zsh_002fzpty-Module zpty] module from [[zsh]]: [http://lilydjwg.is-programmer.com/2011/6/29/using-zpty-module-of-zsh.27677.html]
 
 
 
{{hc|~/.zshrc|
 
<nowiki>zmodload zsh/zpty
 
 
 
pty() {
 
zpty pty-${UID} ${1+$@}
 
if [[ ! -t 1 ]];then
 
setopt local_traps
 
trap '' INT
 
fi
 
zpty -r pty-${UID}
 
zpty -d pty-${UID}
 
}
 
 
 
ptyless() {
 
pty $@ | less
 
}</nowiki>}}
 
 
 
Usage:
 
 
 
$ ptyless ''program''
 
 
 
To pipe it to other pager (less in this example):
 
 
 
$ pty ''program'' | less
 
 
 
== ls ==
 
 
 
[[Wikipedia:ls|ls]] (''list'') is a command to list files in Unix and Unix-like operating systems.
 
 
 
* ''ls'' can list [[File permissions and attributes#Viewing_permissions|file permissions]].
 
 
 
* Colored output can be enabled with a simple alias. File {{ic|~/.bashrc}} should already have the following entry copied from {{ic|/etc/skel/.bashrc}}:
 
: {{ic|1=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:
 
: {{ic|eval $(dircolors -b)}}
 
 
 
== mkdir ==
 
 
 
[[Wikipedia:mkdir|mkdir]] (''make directory'') is a command to create directories.
 
* To create a directory and its whole hierarchy, the {{ic|-p}} switch is used, otherwise an error is printed. As users are supposed to know what they want, {{ic|-p}} switch may be used as a default:
 
: {{bc|1=alias mkdir='mkdir -p -v'}}
 
: The {{ic|-v}} switch make it verbose.
 
 
 
* Changing mode of a just created directory using ''chmod'' is not necessary as the {{ic|-m}} option lets you define the access permissions.
 
 
 
{{Tip|If you just want a temporary directory, a better alternative may be [[Wikipedia:Temporary file|mktemp]] (''make temporary''): {{ic|mktemp -p}}.}}
 
 
 
== mv ==
 
 
 
[[Wikipedia:mv|mv]] (''move'') is a command to move and rename files and directories.
 
* It can be very dangerous so it is prudent to limit its scope:
 
: {{bc|1=alias mv=' timeout 8 mv -iv'}}
 
: This alias suspends ''mv'' after eight 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.
 
 
 
== rm ==
 
 
 
[[Wikipedia:rm_(Unix)|rm]] (''remove'') is a command to delete files and directories.
 
 
 
* It can be very dangerous, so it is prudent to limit its scope:
 
: {{bc|1=alias rm=' timeout 3 rm -Iv --one-file-system'}}
 
: This alias suspends ''rm'' after three seconds, asks confirmation to delete three or more files, lists the operations in progress, does not involve more than one file systems and does not store itself in the shell history file if the shell is configured to ignore space starting commands. Substitute {{ic|-I}} with {{ic|-i}} if you prefer to confirm even for one file.
 
: Zsh users may want to put {{ic|noglob}} before {{ic|timeout}} to avoid implicit expansions.
 
 
 
* To remove directories known to be empty, use ''rmdir'' as it fails in case of files inside the target.
 
 
 
== sed ==
 
 
 
[[Wikipedia:sed|sed]] (''stream editor'') is a Unix utility that parses and transforms text.
 
 
 
Here is a handy [http://sed.sourceforge.net/sed1line.txt list] of ''sed'' one-liners examples.
 
 
 
{{Tip|More powerful alternatives are [[Wikipedia:AWK|AWK]] and even [[Wikipedia:Perl|Perl]] language.}}
 
 
 
== seq ==
 
 
 
'''seq''' (''sequence'') is a utility for generating a sequence of numbers. Shell built-in alternatives are available, so it is good practice to use them as explained on [[Wikipedia:Seq (Unix)|Wikipedia]].
 
 
 
== which ==
 
 
 
The [[wikipedia:Which_(Unix)|which]] command is useful to determine the path to an executable, for example:
 
 
 
# journalctl $(which sshd)
 
 
 
== motd ==
 
 
 
[[Wikipedia:motd (Unix)|motd]] (Message of the day). The  contents  of {{ic|/etc/motd}} are displayed by {{Ic|login(1)}} after a successful login but just before it executes the login shell.
 
 
 
It is a good place to display your Terms of Service to remind users of your local policies or anything you wish to tell them.
 
  
 
== 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] - Overview of commands in coreutils
+
* [https://www.gnu.org/software/coreutils/manual/coreutils.html GNU Coreutils documentation]
 
+
* [http://pubs.opengroup.org/onlinepubs/9699919799/idx/utilities.html POSIX utilities]
* [http://www.gnu.org/software/coreutils/manual/coreutils.html GNU Coreutils Manpage]
 
 
 
* [http://www.linuxquestions.org/questions/linux-newbie-8/learn-the-dd-command-362506/ Learn the DD command]
 

Latest revision as of 03:37, 31 July 2019

Core utilities are the basic, fundamental tools of a GNU/Linux system. On Arch Linux they are found in the base group. This article provides an incomplete overview of them, links their documentation and describes useful alternatives. The scope of this article includes, but is not limited to, the GNU coreutils. Most core utilities are traditional Unix tools (see Heirloom) and many were standardized by POSIX but have been developed further to provide more features.

Most command-line interfaces are documented in man pages, utilities by the GNU Project are documented primarily in Info manuals, some shells provide a help command for shell builtin commands. Additionally most utilities print their usage when run with the --help flag.

Essentials

The following table lists some important utilities which Arch Linux users should be familiar with. See also intro(1).

Package Utility Description Documentation Alternatives
shell built-ins cd change directory cd(1p)
GNU coreutils ls list directory ls(1), info exa, lsd, tree
cat concatenate files to stdout cat(1), info tac(1), bat
mkdir make directory mkdir(1), info
rmdir remove empty directory rmdir(1), info
rm remove files or directories rm(1), info shred
cp copy files or directories cp(1), info
mv move files or directories mv(1), info
ln make hard or symbolic links ln(1), info
chown change file owner and group chown(1), info chgrp(1)
chmod change file permissions chmod(1), info
dd convert and copy a file dd(1), info
df report file system disk space usage df(1), info
GNU tar tar tar archiver tar(1), info archivers
GNU less less terminal pager less(1) terminal pagers
GNU findutils find search files or directories find(1), info, GregsWiki #find alternatives
GNU diffutils diff compare files line by line diff(1), info #diff alternatives
GNU grep grep print lines matching a pattern grep(1), info #grep alternatives
GNU sed sed stream editor sed(1), info, one-liners
GNU gawk awk pattern scanning and processing language gawk(1), info nawk, mawkAUR
util-linux dmesg print or control the kernel ring buffer dmesg(1) systemd journal
lsblk list block devices lsblk(8)
mount mount a filesystem mount(8)
umount unmount a filesystem umount(8)
su substitute user su(1) sudo
kill terminate a process kill(1) pkill(1), killall(1)
procps-ng pgrep look up processes by name or attributes pgrep(1) pidof(1)
ps show information about processes ps(1) top(1), htop
free display amount of free and used memory free(1)

Preventing data loss

rm, mv, cp and shell redirections happily delete or overwrite files without asking. rm, mv, and cp all support the -i flag to prompt the user before every removal / overwrite. Some users like to enable the -i flag by default using aliases. Relying upon these shell options can be dangerous, because you get used to them, resulting in potential data loss when you use another system or user that does not have them. The best way to prevent data loss is to create backups.

Nonessentials

This table lists core utilities that often come in handy.

Package Utility Description Documentation Alternatives
shell built-ins alias define or display aliases alias(1p)
type print the type of a command type(1p) which(1)
time time a command time(1p)
GNU coreutils tee read stdin and write to stdout and files tee(1), info
mktemp make a temporary file or directory mktemp(1), info
cut print selected parts of lines cut(1), info
tr translate or delete characters tr(1), info
od dump files in octal and other formats od(1), info hexdump(1), vim's xxd(1)
sort sort lines sort(1), info
uniq report or omit repeated lines uniq(1), info
comm compare two sorted files line by line comm(1), info
head output the first part of files head(1), info
tail output the last part of files, or follow files tail(1), info
wc print newline, word and byte count wc(1), info
GNU binutils strings print printable characters in binary files strings(1), info
GNU glibc iconv convert character encodings iconv(1) recode
file file guess file type file(1)

The moreutils package provides useful tools like sponge(1) that are missing from the GNU coreutils.

Alternatives

Alternatives to the core utilities in the base group are BusyBox, the Heirloom Toolchest, 9base, sbase-gitAUR and ubase-gitAUR.

cp alternatives

Using rsync#As cp/mv alternative allows you to resume a failed transfer, to show the transfer status, to skip already existing files and to make sure of the destination files integrity using checksums.

find alternatives

  • fd — Simple, fast and user-friendly alternative to find. Ignores hidden and .gitignore'd files by default.
https://github.com/sharkdp/fd || fd
  • fuzzy-find — Fuzzy completion for finding files.
https://github.com/silentbicycle/ff || ff-gitAUR
  • mlocate — Merging locate/updatedb implementation.
https://pagure.io/mlocate || mlocate

For graphical file searchers, see List of applications/Utilities#File searching.

diff alternatives

While diffutils does not provide a word-wise diff, several other programs do:

  • git diff can do a word diff with --color-words, using --no-index it can also be used for files outside of Git working trees.
  • dwdiff — A word diff front-end for the diff program; supports colors.
https://os.ghalkes.nl/dwdiff.html || dwdiff
  • GNU wdiff — A wordwise implementation of GNU diff; does not support colors.
https://www.gnu.org/software/wdiff/ || wdiff
  • cwdiff — A GNU wdiff wrapper that colorizes the output.
https://github.com/junghans/cwdiff || cwdiffAUR, cwdiff-gitAUR
  • icdiff — A colorized diff tool written in Python. "Improved color diff" is meant to supplement normal diff use.
https://github.com/jeffkaufman/icdiff || icdiffAUR,icdiff-gitAUR

See also List of applications/Utilities#Comparison, diff, merge.

grep alternatives

  • mgrep — A multiline grep.
https://sourceforge.net/projects/multiline-grep/ || mgrepAUR

Code searchers

The following three tools aim to replace grep for code search. They do recursive search by default, skip binary files and respect .gitignore.

  • ack — A Perl-based grep replacement, aimed at programmers with large trees of heterogeneous source code.
https://beyondgrep.com/ || ack
  • ripgrep (rg) — A search tool that combines the usability of ag with the raw speed of grep.
https://github.com/BurntSushi/ripgrep || ripgrep
  • The Silver Searcher (ag) — Code searching tool similar to Ack, but faster.
https://github.com/ggreer/the_silver_searcher || the_silver_searcher

Interactive filters

  • fzf — General-purpose command-line fuzzy finder, powered by find by default.
https://github.com/junegunn/fzf || fzf, fzf-gitAUR
  • fzy — A fast, simple fuzzy text selector with an advanced scoring algorithm.
https://github.com/jhawthorn/fzy || fzy, fzy-gitAUR
  • peco — Simplistic interactive filtering tool.
https://github.com/peco/peco || pecoAUR, peco-gitAUR
  • percol — Adds flavor of interactive filtering to the traditional pipe concept of the UNIX shell.
https://github.com/mooz/percol || percol, percol-gitAUR

See also