# Core utilities

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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) | #cd alternatives
GNU coreutils | ls | list directory | ls(1), info | tree, #ls alternatives
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 | #cp alternatives
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, opendoas
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.

### cd alternatives

- zoxide — A smart cd command that learns your habits, allowing you to navigate anywhere in just a few keystrokes.

  https://github.com/ajeetdsouza/zoxide || zoxideAUR

### 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

- broot — A new way to see and navigate directory trees.

  https://github.com/Canop/broot || broot

- exa — Another ls replacement with color support, tree view, git integration and other features.

  https://github.com/ogham/exa || exa

- lsd — Modern ls with a lot of pretty colors and awesome icons.

  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

- plocate — A much faster locate.

  https://plocate.sesse.net/ || plocate

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

- icdiff — A colorized diff tool written in Python. "Improved color diff" is meant to supplement normal diff use.

  https://github.com/jeffkaufman/icdiff || icdiffAUR

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

### grep alternatives

- mgrep — A multiline grep.

  https://sourceforge.net/projects/multiline-grep/ || mgrepAUR

- pdfgrep — A tool to search text in PDF files.

  https://pdfgrep.org/ || pdfgrep

- ripgrep-all — Search in plain text and also in PDFs, E-Books, Office documents, zip, tar.gz.

  https://github.com/phiresky/ripgrep-all || ripgrep-allAUR

#### 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

- fzy — A fast, simple fuzzy text selector with an advanced scoring algorithm.

  https://github.com/jhawthorn/fzy || fzy

- peco — Simplistic interactive filtering tool.

  https://github.com/peco/peco || peco

- percol — Adds flavor of interactive filtering to the traditional pipe concept of the UNIX shell.

  https://github.com/mooz/percol || percol

- skim — Fuzzy finder written in Rust, similar to fzf.

  https://github.com/lotabout/skim || skim

## See also

- GNU Coreutils documentation
- POSIX utilities

Categories:

- Command-line
- Lists of software