-
expr
: perform arithmetic or boolean operations or evaluate regular expressions
-
m4
: simple macro processor
-
yes
: print a string a lot
-
cal
: nice calendar
-
env
: run a command (useful in scripts)
-
printenv
: print out environment variables (useful in debugging and scripts)
-
look
: find English words (or lines in a file) beginning with a string
-
cut
, paste
and join
: data manipulation
-
fmt
: format text paragraphs
-
pr
: format text into pages/columns
-
fold
: wrap lines of text
-
column
: format text fields into aligned, fixed-width columns or tables
-
expand
and unexpand
: convert between tabs and spaces
-
nl
: add line numbers
-
seq
: print numbers
-
bc
: calculator
-
factor
: factor integers
-
toe
: table of terminfo entries
-
nc
: network debugging and data transfer
-
socat
: socket relay and tcp port forwarder (similar to netcat
)
-
dd
: moving data between files or devices
-
file
: identify type of a file
-
tree
: display directories and subdirectories as a nesting tree; like ls
but recursive
-
stat
: file info
-
time
: execute and time a command
-
timeout
: execute a command for specified amount of time and stop the process when the specified amount of time completes.
-
lockfile
: create semaphore file that can only be removed by rm -f
-
logrotate
: rotate, compress and mail logs.
-
watch
: run a command repeatedly, showing results and/or highlighting changes
-
tac
: print files in reverse
-
comm
: compare sorted files line by line
-
strings
: extract text from binary files
-
tr
: character translation or manipulation
-
iconv
or uconv
: conversion for text encodings
-
split
and csplit
: splitting files
-
sponge
: read all input before writing it, useful for reading from then writing to the same file, e.g., grep -v something some-file | sponge some-file
-
units
: unit conversions and calculations; converts furlongs per fortnight to twips per blink (see also /usr/share/units/definitions.units
)
-
apg
: generates random passwords
-
xz
: high-ratio file compression
-
ldd
: dynamic library info
-
nm
: symbols from object files
-
ab
: benchmarking web servers
-
strace
: system call debugging
-
cssh
: visual concurrent shell
-
rsync
: sync files and folders over SSH or in local file system
-
host
and dig
: DNS lookups
-
lsof
: process file descriptor and socket info
-
dstat
: useful system stats
-
iostat
: Disk usage stats
-
mpstat
: CPU usage stats
-
vmstat
: Memory usage stats
-
htop
: improved version of top
-
last
: login history
-
w
: who's logged on
-
id
: user/group identity info
-
ss
: socket statistics
-
dmesg
: boot and system error messages
-
sysctl
: view and configure Linux kernel parameters at run time
-
hdparm
: SATA/ATA disk manipulation/performance
-
lsblk
: list block devices: a tree view of your disks and disk partitions
-
lshw
, lscpu
, lspci
, lsusb
, dmidecode
: hardware information, including CPU, BIOS, RAID, graphics, devices, etc.
-
lsmod
and modinfo
: List and show details of kernel modules.
-
fortune
, ddate
, and sl
: um, well, it depends on whether you consider steam locomotives and Zippy quotations "useful"