sed applies editing commands to each line. The substitute command s/old/new/ replaces the first match per line; g replaces all matches, I ignores case. -i edits the file in place instead of printing the result.
[sed](/man/sed) 's/old/new/g' [file]
[sed](/man/sed) -i 's/old/new/g' [file]
[sed](/man/sed) -i 's/old/new/gI' [file]
sd does the same job with simpler, regex-by-default syntax.
[sd](/man/sd) "old" "new" [file]
Any character can delimit the s command: s|/usr/bin|/usr/local/bin| avoids escaping slashes in paths.
d deletes matching lines; -n with p prints only selected lines. Addresses can be patterns, line numbers, or ranges.
[sed](/man/sed) '/pattern/d' [file]
[sed](/man/sed) -i '/^$/d' [file]
[sed](/man/sed) -n '5,10p' [file]
[sed](/man/sed) -n '/pattern/p' [file]
awk splits every line into fields: $1 is the first field, $0 the whole line, NR the line number. -F changes the field separator from whitespace to anything else.
[awk](/man/awk) '{print $1}' [file]
[awk](/man/awk) -F: '{print $1, $3}' /etc/passwd
[awk](/man/awk) '{print NR, $0}' [file]
cut is the lightweight alternative for simple column extraction, by delimiter (-d, -f) or character position (-c).
[cut](/man/cut) -d: -f1 [file]
[cut](/man/cut) -d',' -f1,3 [file]
[cut](/man/cut) -c1-10 [file]
An awk program is condition { action }: lines matching the condition run the action (default: print the line).
[awk](/man/awk) '$3 > 100' [file]
[awk](/man/awk) '/pattern/ {print $2}' [file]
[awk](/man/awk) 'NR>=5 && NR<=10' [file]
Aggregate across lines with variables and an END block.
[awk](/man/awk) '{sum += $1} END {print sum}' [file]
[awk](/man/awk) '{sum += $1} END {print sum/NR}' [file]
Alphabetical by default; -n sorts numerically, -r reverses, -u drops duplicates, -t and -k sort by a specific field. -h understands human-readable sizes like 2K and 1G.
[sort](/man/sort) [file]
[sort](/man/sort) -n [file]
[sort](/man/sort) -r [file]
[sort](/man/sort) -t: -k3 -n [file]
[sort](/man/sort) -u [file]
uniq only compares neighboring lines, so sort first. -c counts occurrences, -d shows only duplicated lines, -u only unique ones.
[sort](/man/sort) [file] | [uniq](/man/uniq)
[sort](/man/sort) [file] | [uniq](/man/uniq) -c | [sort](/man/sort) -rn
[sort](/man/sort) [file] | [uniq](/man/uniq) -d
The sort | uniq -c | sort -rn pipeline is the classic frequency counter: it ranks every distinct line by how often it occurs.
tr maps characters from one set to another, -d deletes them, -s squeezes repeats into one.
[tr](/man/tr) 'a-z' 'A-Z' < [file]
[tr](/man/tr) -d '[:digit:]' < [file]
[tr](/man/tr) -s ' ' < [file]
[tr](/man/tr) '\n' ' ' < [file]
diff -u is the standard patch-style comparison; -y shows files side by side; cmp compares bytes and is ideal for binary files.
[diff](/man/diff) -u [file1] [file2]
[diff](/man/diff) -y [file1] [file2]
[cmp](/man/cmp) [file1] [file2]
comm shows lines unique to each sorted file and lines they share, in three columns. Suppress columns by number.
[comm](/man/comm) [file1] [file2]
[comm](/man/comm) -12 [file1] [file2]
Both comm and join require their input files to be sorted.
paste glues files together line by line; -s joins all lines of one file into a single line. join matches lines from two files on a common field, like a database join.
[paste](/man/paste) [file1] [file2]
[paste](/man/paste) -d',' [file1] [file2]
[paste](/man/paste) -s [file]
[join](/man/join) [file1] [file2]
[join](/man/join) -t: -1 1 -2 3 [file1] [file2]
Align fields into a table, or wrap long lines. fmt rewraps paragraphs intelligently, fold cuts hard at the width (-s breaks at spaces).
[column](/man/column) -t [file]
[column](/man/column) -t -s',' [file]
[fmt](/man/fmt) -w 80 [file]
[fold](/man/fold) -s -w 80 [file]
nl numbers only non-empty lines by default; -ba numbers all lines, like cat -n.
[nl](/man/nl) [file]
[nl](/man/nl) -ba [file]
[cat](/man/cat) -n [file]
Lines, words, and bytes; -m counts characters in multi-byte encodings.
[wc](/man/wc) [file]
[wc](/man/wc) -l [file]
[wc](/man/wc) -w [file]
[wc](/man/wc) -c [file]
tac prints a file last line first, rev reverses each line's characters, shuf randomizes line order.
[tac](/man/tac) [file]
[rev](/man/rev) [file]
[shuf](/man/shuf) [file]
[shuf](/man/shuf) -n 1 [file]