Bash Operator Cheatsheet

-e

File exists (any type)

[[ -e file.txt ]]

-f

File exists and is a regular file

[[ -f script.sh ]]

-d

File exists and is a directory

[[ -d myfolder ]]

-r

File is readable

[[ -r data.txt ]]

-w

File is writable

[[ -w output.log ]]

-x

File is executable

[[ -x script.sh ]]

-s

File exists and is not empty

[[ -s nonempty.txt ]]

-L

File is a symbolic link

[[ -L shortcut ]]

-b

File is a block device

[[ -b /dev/sda1 ]]

-c

File is a character device

[[ -c /dev/ttyS0 ]]

-p

File is a named pipe (FIFO)

[[ -p pipefile ]]

-S

File is a socket

[[ -S /var/run/docker.sock ]]

-z

String is empty

[[ -z "$var" ]]

-n

String is not empty

[[ -n "$var" ]]

=

Strings are equal

[[ "$a" = "$b" ]]

!=

Strings are not equal

[[ "$a" != "$b" ]]

>

String a is greater than b (lexically)

[[ "$a" > "$b" ]]

<

String a is less than b (lexically)

[[ "$a" < "$b" ]]

-eq

Equal to

[[ "$a" -eq "$b" ]]

-ne

Not equal to

[[ "$a" -ne "$b" ]]

-lt

Less than

[[ "$a" -lt "$b" ]]

-le

Less than or equal to

[[ "$a" -le "$b" ]]

-gt

Greater than

[[ "$a" -gt "$b" ]]

-ge

Greater than or equal to

[[ "$a" -ge "$b" ]]

&&

Logical AND (both must be true)

[[ -f file.txt && -r file.txt ]]

||

Logical OR (either can be true)

[[ -d mydir || -f myfile ]]

!

Logical NOT (negation)

[[ ! -e missing.txt ]]

-a

Logical AND (deprecated)

[[ -f file.txt -a -r file.txt ]]

-o

Logical OR (deprecated)

[[ -d mydir -o -f myfile ]]

+

Addition

sum = a + b

-

Subtraction

diff = a - b

*

Multiplication

product = a * b

/

Division

quotient = a / b

%

Modulus (remainder)

remainder = a % b

**

Exponentiation

power = a ** b

++

Increment

a++

--

Decrement

b--

=

Assign value

a=5

+=

Add and assign

a+=2 # a = a + 2

-=

Subtract and assign

b-=3 # b = b - 3

*=

Multiply and assign

c*=4 # c = c * 4

/=

Divide and assign

d/=2 # d = d / 2

%=

Modulus and assign

e%=3 # e = e % 3

**=

Exponentiate and assign

f=2 # f = f 2

&

AND

result = a & b

|

OR

result = a | b

^

XOR

result = a ^ b

~

NOT

result = ~a

<<

Left shift

result = a << 2

>>

Right shift

result = a

;

Run multiple commands sequentially

echo "Hello"; echo "World"

&

Run command in the background

sleep 10 &

&&

Run next command if previous succeeds

mkdir test && cd test

`

`

Run next command if previous fails

`rm file

echo "File not found"`

`

`

Pipe output of one command to another

`ls -l

grep ".txt"`

>

Redirect output to a file (overwrite)

echo "Hello" > file.txt

>>

Redirect output to a file (append)

echo "World" >> file.txt

<

Read input from a file

sort < input.txt

2>

Redirect stderr to a file

command 2> error.log

2>&1

Redirect stderr to stdout

command > output.log 2>&1

&>

Redirect both stdout and stderr to a file

command &> log.txt

$(command)

Command substitution

current_date=$(date)

Arithmetic evaluation

result = a + b

[[ ]]

Advanced test command

[[ -f file.txt ]]

{ }

Group commands in the current shell

{ echo "One"; echo "Two"; }

( )

Group commands in a subshell

(cd /tmp; ls)