Section 1 of the manual describes user commands and tools, for example, file manipulation tools, shells, compilers, web browsers, file and image viewers and editors, and so on.

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apngasm
assemble individual PNG files int to animated PNG file
apngdis
deconstruct APNG file into a sequence of PNG frames
apngopt
optimize animated PNG image files
apol
Graphical SELinux policy analysis tool  
apop_db_to_crosstab
command line utility to convert a three-column table to a crosstab
apop_plot_query
command line utility to take in a query and put out a Gnuplot table file
apop_text_to_db
command line utility to convert a text file into a database table
apparix
augmenting cd with bookmarks
append_sff
combine multiple SFF files
appendpdf
Append one PDF to another
apper
An application and package manager using PackageKit
appfeed.cgi
Xymon CGI feeder for Smartphone apps
apply-multiarch-hints
apply multi-arch hints
applyBoundaryLayer
part of OpenFOAM (The Open Source CFD Toolbox)
apply_diff_relay_logs
Generating differential relay logs between the latest slave and target slave, and applying all binlog/relay log files. This command is automatically executed from MHA Manager on failover, and manual execution should not be needed normally
applycal
Apply - Apply device calibration to an ICC profile
applygeo
apply georeferencing to an existing file  
applypatch
apply 'makepatch' generated script to update a source tree
applyplugin
apply LADSPA plugin to an audio file
appres
list X application resource database
apprise
Push Notifications that work with just about every platform!
appstream-compose
Generate AppStream metadata
appstream-generator
Generate AppStream metadata from distribution repositories
appstream-util
Manipulate AppStream, AppData and MetaInfo metadata
appstreamcli-compose
Compose AppStream metadata catalog from directory trees
appstreamcli
Handle AppStream metadata formats and query AppStream data
apr-1-config
Return metainformation about apr library
apr-config
apr-1-config - Return metainformation about apr library
apriboot
rewrite disc boot sector, converting between Apricot and PCDOS
aprofutil
Mono's AOT profile tool
apropos
search the manual page names and descriptions
aps2file
printing to a file via apsfilter
apsfilter-bug
create a half-automatic bug report for apsfilter
apsfilter
magic print filter with auto file type recognition
apspreview
preview PostScript file(s) as generated by apsfilter
apt-add-repository
add-apt-repository - Adds a repository into the /etc/apt/sources.list or /etc/apt/sources.list.d or removes an existing one
apt-build
Fetch sources and build packages optimized for your architecture
apt-cudf
CUDF solver integration for APT
apt-dater-host
host helper application for apt-dater
apt-extracttemplates
Utility to extract debconf config and templates from Debian packages
apt-file
- APT package searching utility -- command-line interface
apt-ftparchive
Utility to generate index files
apt-get-build-depends
apt-get install build depends  
apt-listbugs
Lists critical bugs before each APT installation/upgrade
apt-listchanges
Show new changelog entries from Debian package archives
apt-listdifferences
source differences notification tool
apt-mirror
apt sources mirroring tool
apt-rdepends
performs recursive dependency listings similar to apt-cache
apt-show-source
Lists source-packages
apt-show-versions
Lists available package versions with distribution
apt-sortpkgs
Utility to sort package index files
apt-src
manage debian source package trees
apt-transport-http
APT transport for downloading via the Hypertext Transfer Protocol (HTTP)
apt-transport-https
APT transport for downloading via the HTTP Secure protocol (HTTPS)
apt-transport-mirror
APT transport for more automated mirror selection
apt-venv
apt virtual environment
apticron
Generate a mail listing packages which are pending an upgrade
aptitude-create-state-bundle
bundle the current aptitude state
aptitude-run-state-bundle
unpack an aptitude state bundle and invoke aptitude on it
aptly-publisher
tool for easy creation of Aptly multi component publishes
aptly
Debian repository management tool
apulse
The PulseAudio emulator for ALSA
apvlv
PDF/DJVU/EPUB/HTML/TXT viewer with vim-like behaviour
apwal
powerful application launcher
apxs
APache eXtenSion tool  
apxs2
apxs - APache eXtenSion tool  
aqemu
frontend for qemu
aqhbci-tool4
Command line tools for setup, modification and debugging of HBCI settings
ar
create, modify, and extract from archives
ar
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux
ar86
Create, modify, and extract from archive file
arachne-pnr
Place and route tool for iCE40 family FGPAs
aragorn
detect tRNA genes in nucleotide sequences
arancid
rancid - Cisco configuration filter
arandr
visual front end for XRandR 1.2
aranym-jit
ARAnyM - Atari Running on Any Machine - JIT enabled
aranym-mmu
ARAnyM - Atari Running on Any Machine with 68040 MMU enabled
aranym
ARAnyM - Atari Running on Any Machine
arara
a TeX automation tool based on rules and directives
aratapif
ARanyM - Atari Running on Any Machine - aratapif
arb-kill
definitely kill all processes started by arb that are started by the user   If option --all is given try sudo to kill all processes even if they are owned by other users.  
arb
phylogenetic sequence analysis suite
arb_clean
clean processes started by arb that are started by the user  
arborist
index.js - the npm tree doctor
arc-config-check
checks the arc.conf for inconsistencies, known problems or bad taste.  
arc-linux-gnu-addr2line
addr2line - convert addresses or symbol+offset into file names and line numbers
arc-linux-gnu-ar
ar - create, modify, and extract from archives
arc-linux-gnu-as
AS - the portable GNU assembler
arc-linux-gnu-c++filt
c++filt - demangle C++ and Java symbols
arc-linux-gnu-elfedit
elfedit - update ELF header and program property of ELF files
arc-linux-gnu-gcc-ar-12
gcc-ar - a wrapper around ar adding the --plugin option  
arc-linux-gnu-gcc-ar
gcc-ar - a wrapper around ar adding the --plugin option  
arc-linux-gnu-gcc-nm-12
gcc-nm - a wrapper around nm adding the --plugin option  
arc-linux-gnu-gcc-nm
gcc-nm - a wrapper around nm adding the --plugin option  
arc-linux-gnu-gcc-ranlib-12
gcc-ranlib - a wrapper around ranlib adding the --plugin option  
arc-linux-gnu-gcc-ranlib
gcc-ranlib - a wrapper around ranlib adding the --plugin option  
arc-linux-gnu-gm2-12
gm2 - The GNU Modula-2 Compiler
arc-linux-gnu-gm2
gm2 - The GNU Modula-2 Compiler
arc-linux-gnu-gprof
gprof - display call graph profile data
arc-linux-gnu-ld
ld - The GNU linker