| Command | Description | Example | |
| & | Run the previous command in the background | ls & | |
| && | Logical AND | if [ “$foo” -ge “0” ] && [ “$foo” -le “9”] | |
| || | Logical OR | if [ “$foo” -lt “0” ] || [ “$foo” -gt “9” ] (not in Bourne shell) | |
| ^ | Start of line | grep ”^foo” | |
| $ | End of line | grep “foo$” |
| = | String equality (cf. -eq) | if [ “$foo” = “bar” ] | |
| ! | Logical NOT | if [ “$foo” != “bar” ] | |
| $$ | PID of current shell | echo “my PID = $$” | |
| $! | PID of last background command | ls & echo “PID of ls = $!” | |
| $? | exit status of last command | ls ; echo “ls returned code $?” | |
| $0 | Name of current command (as called) | echo “I am $0” | |
| $1 | Name of current command's first parameter | echo “My first argument is $1” | |
| $9 | Name of current command's ninth parameter | echo “My ninth argument is $9” | |
| $@ | All of current command's parameters (preserving whitespace and quoting) | echo “My arguments are $@” | |
| $* | All of current command's parameters (not preserving whitespace and quoting) | echo “My arguments are $*” | |
| parenthesis: ( … ) | Function definition | function myfunc() { echo hello } | |
| -b | block special file | if [ -b filename ] | |
| -c | Special character file | if [ -c filename ] | |
| -d | Is a Directory | if [ -d /bin ] | |
| -e | Is file exist | if [ -e /bin/ls ] | |
| -eq | Numeric Equality | if [ “$foo” -eq “9” ] | |
| -f | Is a File | if [ -f /bin/ls ] | |
| -G | check if file exists and is owned by effective groupid | if [ -G /bin/ls ] | |
| -g | true if file exists and is set-group-id | if [ -g /bin/ls ] | |
| -ge | Greater Than or Equal | if [ “$foo” -ge “9” ] | |
| -gt | Greater Than | if [ “$foo” -gt “9” ] | |
| -k | check sticky bit | if [ -k /bin/ls ] | |
| -L | if file a symbolic link | if [ -L /etc/alternatives/editor ] | |
| -le | Less Than or Equal | if [ “$foo” -le “9” ] | |
| -lt | Less Than | if [ “$foo” -lt “9” ] | |
| -n | String is not zero length | if [ -n “$foo” ] | |
| -ne | Not Equal | if [ “$foo” -ne “9” ] | |
| -nt | Newer Than | if [ “$file1” -nt “$file2” ] | |
| -O | True if file exists and is owned by the effective user id | if [ -O file ] | |
| -r | Is a readable file | if [ -r /bin/ls ] | |
| -s | if file is nonzero size | if [ -s /bin/ls ] | |
| -S | if file is a socket | if [ -S file ] | |
| -u | check if file set-user-id bit is set | if [ -u /bin/ls ] | |
| -w | Is a writable file | if [ -w /bin/ls ] | |
| -x | Is an executable file | if [ -x /bin/ls ] | |
| -z | String is zero length | if [ -z “$foo” ] | |