bash-tests.sh

[ "$#" -t 0 ] && echo "Not piped"

# ───────── STRING TESTS ─────────

[ -z "$var" ]            # true if string is empty or unset
[ -n "$var" ]            # true if string is non-empty

[ "$a" = "$b" ]          # true if strings are equal
[ "$a" != "$b" ]         # true if strings are not equal

[ "$a" \< "$b" ]         # true if a sorts before b (lexicographically)
[ "$a" \> "$b" ]         # true if a sorts after b

# ───────── NUMERIC TESTS ─────────

[ "$a" -eq "$b" ]        # equal
[ "$a" -ne "$b" ]        # not equal
[ "$a" -lt "$b" ]        # less than
[ "$a" -le "$b" ]        # less than or equal
[ "$a" -gt "$b" ]        # greater than
[ "$a" -ge "$b" ]        # greater than or equal

# ───────── FILE TESTS ─────────

[ -e "$file" ]           # file exists
[ -f "$file" ]           # regular file
[ -d "$file" ]           # directory
[ -L "$file" ]           # symbolic link
[ -p "$file" ]           # named pipe
[ -S "$file" ]           # socket
[ -b "$file" ]           # block device
[ -c "$file" ]           # character device

[ -r "$file" ]           # readable
[ -w "$file" ]           # writable
[ -x "$file" ]           # executable

[ -s "$file" ]           # file exists and is not empty
[ -O "$file" ]           # owned by current user
[ -G "$file" ]           # owned by current group
[ -u "$file" ]           # setuid bit set
[ -g "$file" ]           # setgid bit set
[ -k "$file" ]           # sticky bit set

[ "$f1" -nt "$f2" ]      # f1 newer than f2
[ "$f1" -ot "$f2" ]      # f1 older than f2
[ "$f1" -ef "$f2" ]      # same inode

# ───────── VARIABLE / PARAMETER TESTS ─────────

[ -v var ]               # variable var is set (bash ≥4.2)
[ -R var ]               # variable is a nameref
[ -t 0 ]                 # stdin is a terminal
[ -t 1 ]                 # stdout is a terminal

# ───────── LOGICAL OPERATORS ─────────

[ cond1 ] && [ cond2 ]   # AND
[ cond1 ] || [ cond2 ]   # OR
[ ! cond ]               # NOT

# ───────── ARITHMETIC ((( ))) ─────────

(( a == b ))             # equal
(( a != b ))             # not equal
(( a < b ))              # less than
(( a <= b ))             # less than or equal
(( a > b ))              # greater than
(( a >= b ))             # greater than or equal

(( a ))                  # true if non-zero
(( !a ))                 # true if zero

# ───────── [[ ]] EXTENDED TESTS (BASH) ─────────

[[ -z $var ]]            # empty
[[ -n $var ]]            # non-empty

[[ $a == $b ]]           # string equal
[[ $a != $b ]]           # string not equal
[[ $a < $b ]]            # lexicographically less
[[ $a > $b ]]            # lexicographically greater

[[ $var == *.txt ]]      # glob match
[[ $var =~ regex ]]     # regex match

[[ -e $file ]]           # file exists
[[ -f $file ]]           # regular file
[[ -d $file ]]           # directory

# ───────── COMMAND STATUS ─────────

command                    # run command
[ $? -eq 0 ]               # previous command succeeded
[ $# != 4 ]               # compare number of args passed

command && echo ok         # success
command || echo fail       # failure

# ───────── EXIT STATUS SHORTCUTS ─────────

true                      # always true (exit 0)
false                     # always false (exit 1)