Difference between revisions of "Core utilities"

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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 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.
 
  
== cat ==
+
''Core utilities'' are the basic, fundamental tools of a [[GNU]]/[[Linux]] system. 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.
  
[[Wikipedia:cat_(Unix)|cat]] (''catenate'') is a standard Unix utility that concatenates and lists files.
+
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.
  
* 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''}}.
+
== Essentials ==
  
* ''cat'' is able to work with multiple lines, although this is sometimes regarded as bad practice:
+
The following table lists some important utilities which Arch Linux users should be familiar with. See also {{man|1|intro}}.
  
{{bc|
+
{| class=wikitable
$ cat << EOF >> ''path/file''
+
! Package !! Utility !! Description !! Documentation !! Alternatives
''first line''
+
|-
...
+
| shell built-ins || cd || change directory || {{man|1p|cd}}
''last line''
+
|-
EOF
+
|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}}
: A better alternative is the ''echo'' command:
+
|-
{{bc|
+
| 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}}
$ echo "\
+
|-
''first line''
+
| mkdir || make directory || {{man|1|mkdir}}, [https://www.gnu.org/software/coreutils/manual/html_node/mkdir-invocation.html info]
...
+
|-
''last line''" \
+
| rmdir || remove empty directory || {{man|1|rmdir}}, [https://www.gnu.org/software/coreutils/manual/html_node/rmdir-invocation.html info]
>> ''path/file''
+
|-
}}
+
| rm || remove files or directories || {{man|1|rm}}, [https://www.gnu.org/software/coreutils/manual/html_node/rm-invocation.html info] || [[shred]]
 
+
|-
* If you need to list file lines in reverse order, there is a utility called [[Wikipedia:tac (Unix)|tac]] (''cat'' reversed).
+
| cp || copy files or directories || {{man|1|cp}}, [https://www.gnu.org/software/coreutils/manual/html_node/cp-invocation.html info]
 
+
|-
== cron ==
+
| mv || move files or directories || {{man|1|mv}}, [https://www.gnu.org/software/coreutils/manual/html_node/mv-invocation.html info]
 
+
|-
[[Wikipedia:cron|cron]] is a time-based job scheduler in Unix-like computer operating systems.
+
| ln || make hard or symbolic links || {{man|1|ln}}, [https://www.gnu.org/software/coreutils/manual/html_node/ln-invocation.html info]
 
+
|-
See the [[cron|main article]].
+
| [[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}}
{{Note|''systemd'' is able to handle many ''cron'' use cases. See the [[systemd/cron_functionality|related article]].}}
+
|-
 
+
| [[chmod]] || change file permissions || {{man|1|chmod}}, [https://www.gnu.org/software/coreutils/manual/html_node/chmod-invocation.html info]
== dd ==
+
|-
 
+
| [[dd]] || convert and copy a file || {{man|1|dd}}, [https://www.gnu.org/software/coreutils/manual/html_node/dd-invocation.html info]
[[Wikipedia:dd (Unix)|dd]] is a command on Unix and Unix-like operating systems whose primary purpose is to convert and copy a file.
+
|-
 
+
| df || report file system disk space usage || {{man|1|df}}, [https://www.gnu.org/software/coreutils/manual/html_node/df-invocation.html info]
{{Note|''cp'' does the same as ''dd'' without any operands but is not designed for more versatile disk wiping procedures.}}
+
|-
 +
| GNU {{Pkg|tar}} || [[tar]] || tar archiver || {{man|1|tar}}, [https://www.gnu.org/software/tar/manual/html_chapter/index.html info] || [[archiver]]s
 +
|-
 +
| GNU {{Pkg|less}} || less || terminal pager || {{man|1|less}} || [[terminal pager]]s
 +
|-
 +
| 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]]
 +
|-
 +
| 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]]
 +
|-
 +
| 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]]
 +
|-
 +
| 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]
 +
|-
 +
| 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}}
 +
|-
 +
|rowspan=6| {{Pkg|util-linux}}
 +
| [[Wikipedia:dmesg|dmesg]] || print or control the kernel ring buffer || {{man|1|dmesg}} || [[systemd journal]]
 +
|-
 +
| [[lsblk]] || list block devices || {{man|8|lsblk}}
 +
|-
 +
| [[mount]] || mount a filesystem || {{man|8|mount}}
 +
|-
 +
| [[umount]] || unmount a filesystem || {{man|8|umount}}
 +
|-
 +
| [[su]] || substitute user || {{man|1|su}} || [[sudo]]
 +
|-
 +
| 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}}
 +
|}
  
=== Checking progress of dd while running ===
+
=== Preventing data loss ===
  
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:
+
{{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.
# killall -USR1 dd
 
  
{{Note|This will affect all other running ''dd'' processes as well.}}
+
== Nonessentials ==
  
Or:
+
This table lists core utilities that often come in handy.
# kill -USR1 ''pid_of_dd_command''
 
  
For example:
+
{| class=wikitable
# kill -USR1 $(pidof dd)
+
! Package !! Utility !! Description !! Documentation !! Alternatives
 
 
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
 
 
 
=== dd spin-offs ===
 
 
 
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's 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 ===
 
 
 
Beyond aesthetics, ''grep''&#39;s color output is immensely useful for learning [[Wikipedia:regexp|regexp]] and ''grep''&#39;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'}}
 
Alternatively, you can set the {{ic|GREP_OPTIONS}} [[Environment variables|environment variable]] bearing in mind this may break some scripts that use ''grep'' [http://brainstorm.ubuntu.com/idea/24141/]:
 
export GREP_OPTIONS='--color=auto'
 
To include file line numbers in the output, add {{ic|-n}}:
 
alias grep='grep -n --color=auto'
 
 
 
The environment variable {{ic|GREP_COLORS}} may be used to specify different colors than the defaults.
 
 
 
== 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}}:
 
 
 
$ iconv -f ISO-8859-15 -t UTF-8 foo >foo.utf
 
 
 
See {{ic|man iconv}} for more 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 pages 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].
 
 
 
=== Colored output through environment variables ===
 
  
Add the following lines to your shell configuration file:
+
== Alternatives ==
  
{{hc|~/.bashrc|2=
+
Alternative core utilities are provided by [[BusyBox]], the [[Heirloom|Heirloom Toolchest]], {{Pkg|9base}}, {{AUR|sbase-git}} and {{AUR|ubase-git}}.
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: [[Wikipedia:ANSI_escape_code#Colors|ANSI escape code]].
+
=== cp alternatives ===
  
=== Colored output through wrappers ===
+
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.
  
You can enable code syntax coloring in ''less''. First, install {{Pkg|source-highlight}}, then add these lines to your shell configuration file:
+
=== ls 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}}.
+
* {{App|lsd|Modern ls with a lot of pretty colors and awesome icons. Written in Rust.|https://github.com/Peltoche/lsd|{{Pkg|lsd}}}}
  
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|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 ===
  
=== Get colored output when pipe STDOUT of a program to less ===
+
* {{App|mgrep|A multiline grep.|https://sourceforge.net/projects/multiline-grep/|{{AUR|mgrep}}}}
{{note|It's recommend to add [[#Colored_output_through_environment_variables|this above]] to your {{ic|~/.bashrc}} or {{ic|~/.zshrc}}. Because this section is totally written based on this: {{ic|1=export LESS=R}}}}
 
When we run a command and piping its STDOUT to {{ic|less}} for a paged view(e.g. {{ic|<nowiki>yaourt -Qe --date|less</nowiki>}}), you may found that the output is not colored any more. This is usually because the program try to detect the STDOUT whether is a interactive tty: if the STDOUT is to a interactive tty, then the program will print colored output, if not it prints uncolored output.
 
This is totally a good behaviour when you want to redirect(write) the STDOUT to a file as a log(e.g. {{ic|<nowiki>yaourt -Qe --date > pkglst-backup.txt</nowiki>}}). However, this will not be a good behaviour when you want to view the output in {{ic|less}}. Some programs provide a option to disable the interactive tty detection, like this one:
 
{{bc|<nowiki># dmesg --color=always | less</nowiki>}}
 
However there are also some programs haven't provided similar option yet, in this case we need some trick on [[Wikipedia:Pseudo_terminal|pty]] which can make the program believe that the STDOUT is a interactive tty. There are several method available, choose one your favourite:
 
  
1. [https://github.com/lilydjwg/stdoutisatty/blob/master/libstdoutisatty.c stdoutisatty] is a little C implement can invoke a 'fake interactive tty'. Before use this you need  to install it (aur/{{aur|stdoutisatty-git}}), the usage looks like this:
+
==== Code searchers ====
{{bc|<nowiki>$ stdoutisatty yaourt -Qe --date | less</nowiki>}}
 
  
2. [http://www.dest-unreach.org/socat/doc/README socat] is a relay for bidirectional data transfer between two independent data channels. It based on GNU readline and available in offical repository ({{pkg|socat}} is in [extra]), the usage our needed is like:
+
The following three tools aim to replace grep for code search. They do recursive search by default, skip binary files and respect {{ic|.gitignore}}.
{{bc|<nowiki>$ socat EXEC:"yaourt -Qe --date",pty STDIO | less</nowiki>}}
 
  
3. [http://man7.org/linux/man-pages/man1/script.1.html script] is an old enough command that make typescript of terminal session, the usage in this section looks like:<br>{{bc|<nowiki>$ script -fqc 'yaourt -Qe --date' | less</nowiki>}}
+
* {{App|ack|A Perl-based grep replacement, aimed at programmers with large trees of heterogeneous source code.|https://beyondgrep.com/|{{Pkg|ack}}}}
{{tip|Perhaps this helper function from [http://stackoverflow.com/questions/1401002/trick-an-application-into-thinking-its-stdin-is-interactive-not-a-pipe/20401674#20401674 stackoverflow] will be useful:<br>{{bc|
+
* {{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}}}}
function faketty {script -qfc "$(printf "'%s' " "$@")"}
+
* {{App|The Silver Searcher (ag)|Code searching tool similar to Ack, but faster.|https://github.com/ggreer/the_silver_searcher|{{Pkg|the_silver_searcher}}}}
}}}}
 
  
4. [http://expect.sourceforge.net/example/unbuffer.man.html unbuffer] is a good (its man page is even longer than the program itself), old script based on sh and [http://tcl.tk/ Tcl]. It can do the trick well, {{ic|unbuffer}} comes with {{pkg|expect}}. The usage what we need is looks like this,
+
==== Interactive filters ====
{{bc|<nowiki>$ unbuffer yaourt -Qe --date | less</nowiki>}}
 
  
5. [http://zsh.sourceforge.net/Doc/Release/Zsh-Modules.html#The-zsh_002fzpty-Module zpty] is a module of [[zsh]], here is a tiny function from [http://lilydjwg.is-programmer.com/2011/6/29/using-zpty-module-of-zsh.27677.html], put it in your {{ic|~/.zshrc}}:
+
* {{App|[[fzf]]|General-purpose command-line fuzzy finder, powered by find by default.|https://github.com/junegunn/fzf|{{Pkg|fzf}}, {{AUR|fzf-git}}}}
{{bc|ptyless() {
+
* {{App|fzy|A fast, simple fuzzy text selector with an advanced scoring algorithm.|https://github.com/jhawthorn/fzy|{{Pkg|fzy}}, {{AUR|fzy-git}}}}
zmodload zsh/zpty
+
* {{App|peco|Simplistic interactive filtering tool.|https://github.com/peco/peco|{{AUR|peco}}, {{AUR|peco-git}}}}
zpty ptyless ${1+"$@"}           # ptyless, name of pty
+
* {{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}}}}
zpty -r ptyless > /tmp/ptyless.$$ # Write to file, just dunno why pipeline doesn't work fine here
 
less /tmp/ptyless.$$
 
rm -f /tmp/ptyless.$$
 
zpty -d ptyless                  # remove used pty
 
}
 
}}
 
Usage is:
 
{{bc|<nowiki>$ ptyless yaourt -Qe --date | less</nowiki>}}
 
 
 
== locate ==
 
 
 
[[Wikipedia:locate (Unix)|locate]] serves to find files on filesystems. It searches through a prebuilt database of files generated by ''updatedb'' or by a daemon and compressed using incremental encoding. It operates significantly faster than ''find'', but requires regular updating of the database.
 
 
 
See the [[locate|main article]].
 
 
 
== 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)}}
 
 
 
== man ==
 
 
 
[[Wikipedia:Man page|man]] (''manual page'') is a form of online software documentation usually found on a Unix or Unix-like operating system. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts. See [[Man Pages]].
 
 
 
== mkdir ==
 
 
 
[[Wikipedia:mkdir|mkdir]] (''make directory'') is a command to create directories.
 
* To create a directory and its whole hierarchy, {{ic|-p}} switch is used, if not a 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 termporary''): {{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:
 
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]].
 
 
 
== shred ==
 
 
 
[[Wikipedia:Shred_(Unix)|shred]] is a Unix command that can be used to securely delete files and devices so that they can be recovered only with great difficulty with specialised hardware, if at all. ''shred'' uses three passes, writing [[Random number generation|pseudo-random data]] to the device during each pass. This can be reduced or increased.
 
 
 
The following command invokes shred with its default settings and displays the progress.
 
# shred -v /dev/sd''X''
 
 
 
Alternatively, shred can be instructed to do only one pass, with entropy from e.g. {{ic|/dev/urandom}}.
 
# shred --verbose --random-source=/dev/urandom -n1 /dev/sd''X''
 
 
 
''shred'' can be very dangerous so it is prudent to limit its scope:
 
alias shred=' timeout 3 shred -v'
 
 
 
This alias suspends ''shred'' after three seconds, 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.
 
 
 
Zsh users may want to put {{ic|noglob}} before {{ic|timeout}} to avoid implicit expansions.
 
 
 
== sudo ==
 
 
 
[[Wikipedia:Sudo|Sudo]] (''as superuser do'') is a program for Unix-like computer operating systems that allows users to run programs with the security privileges of another user (normally the superuser, or root). See [[Sudo]].
 
 
 
== Permissions related utilities ==
 
 
 
* [[Wikipedia:chmod|chmod]] (''change mode'') is the name of a Unix shell command and a system call, which both change the access permissions to file system objects (including files and directories), as well as specifying special flags.
 
 
 
* [[Wikipedia:chown|chown]] (''change owner'') is used on Unix-like systems to change the owner of a file.
 
 
 
* [[Wikipedia:chattr|chattr]] (''change attributes'') is a command in the Linux operating system that allows a user to set certain attributes on a file residing on many Linux filesystems.
 
 
 
* [[Wikipedia:lsattr|lsattr]] (''list attributes'') is a command-line program for listing the attributes on a Linux extended file system.
 
 
 
* {{ic|ls -l}} lists files attributes.
 
 
 
These utilities are explained in the [[File permissions and attributes]] article. More advanced permission use cases are satisfied by [[Using File Capabilities Instead Of Setuid|capabilities]] and [[ACL]].
 
  
 
== 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 17:02, 9 October 2019

Core utilities are the basic, fundamental tools of a GNU/Linux system. 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

Alternative core utilities are provided by 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.

ls alternatives

  • lsd — Modern ls with a lot of pretty colors and awesome icons. Written in Rust.
https://github.com/Peltoche/lsd || lsd

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