dark

test – Execute the Conditional Expression

The test command is a built-in command in Linux that evaluates the conditional expression and returns a true or false value. It is also known as [ command as it is implemented as a symbolic link to the test command. The command is commonly used in shell scripts to test the values of variables or files.

Overview

The test command is used to evaluate conditional expressions and return a true or false value. The syntax of the test command is as follows:

test EXPRESSION

The EXPRESSION can be any of the following:

  • String Comparison: string1 = string2, string1 != string2, string1 < string2, string1 > string2, string1 -n string2, string1 -z string2
  • File Comparison: file1 -ef file2, file1 -nt file2, file1 -ot file2, -b file, -c file, -d file, -e file, -f file, -g file, -h file, -k file, -p file, -r file, -s file, -t file, -u file, -w file, -x file, -O file, -G file
  • Numeric Comparison: num1 -eq num2, num1 -ne num2, num1 -lt num2, num1 -le num2, num1 -gt num2, num1 -ge num2
  • Logical Operators: ! EXPRESSION, EXPRESSION1 -a EXPRESSION2, EXPRESSION1 -o EXPRESSION2

The test command returns a true (0) or false (1) value based on the evaluation of the EXPRESSION. A true value means that the expression is true, and a false value means that the expression is false.

Examples:

To check if a file exists, you can use the following command:

test -e /path/to/file && echo "File exists" || echo "File does not exist"

To check if a string is empty, you can use the following command:

test -z "$string" && echo "String is empty" || echo "String is not empty"

To check if a number is greater than or equal to another number, you can use the following command:

test "$num1" -ge "$num2" && echo "num1 is greater than or equal to num2" || echo "num1 is less than num2"

Options

The test command does not have any options. However, since it is implemented as a symbolic link to the test command, it supports all the options of the test command.

The following table lists all the available options for the test command:

Option Description
-b FILE True if FILE exists and is a block special file.
-c FILE True if FILE exists and is a character special file.
-d FILE True if FILE exists and is a directory.
-e FILE True if FILE exists.
-f FILE True if FILE exists and is a regular file.
-g FILE True if FILE exists and is set-group-ID.
-h FILE True if FILE exists and is a symbolic link.
-k FILE True if FILE exists and its “sticky” bit is set.
-p FILE True if FILE exists and is a named pipe (FIFO).
-r FILE True if FILE exists and is readable.
-s FILE True if FILE exists and has a size greater than zero.
-t FD True if file descriptor FD is open and refers to a terminal.
-u FILE True if FILE exists and its set-user-ID bit is set.
-w FILE True if FILE exists and is writable.
-x FILE True if FILE exists and is executable.
-O FILE True if FILE exists and is owned by the effective user ID.
-G FILE True if FILE exists and is owned by the effective group ID.
FILE1 -ef FILE2 True if FILE1 and FILE2 refer to the same device and inode numbers.
FILE1 -nt FILE2 True if FILE1 is newer than FILE2.
FILE1 -ot FILE2 True if FILE1 is older than FILE2.
STRING1 = STRING2 True if the strings are equal.
STRING1 != STRING2 True if the strings are not equal.
STRING1 < STRING2 True if STRING1 is less than STRING2.
STRING1 > STRING2 True if STRING1 is greater than STRING2.
-n STRING True if the length of STRING is non-zero.
-z STRING True if the length of STRING is zero.
NUM1 -eq NUM2 True if NUM1 is equal to NUM2.
NUM1 -ne NUM2 True if NUM1 is not equal to NUM2.
NUM1 -lt NUM2 True if NUM1 is less than NUM2.
NUM1 -le NUM2 True if NUM1 is less than or equal to NUM2.
NUM1 -gt NUM2 True if NUM1 is greater than NUM2.
NUM1 -ge NUM2 True if NUM1 is greater than or equal to NUM2.
! EXPRESSION True if EXPRESSION is false.
EXPRESSION1 -a EXPRESSION2 True if both EXPRESSION1 and EXPRESSION2 are true.
EXPRESSION1 -o EXPRESSION2 True if either EXPRESSION1 or EXPRESSION2 is true.

Troubleshooting Tips

  • If you are getting unexpected results, double-check the syntax of the EXPRESSION.
  • When using variables in the EXPRESSION, make sure to enclose them in double-quotes to prevent word splitting and globbing.
  • When using the -n or -z options, make sure to enclose the STRING in double-quotes to prevent globbing.

Notes

  • The test command is often used in shell scripts to test the values of variables or files.
  • The test command is implemented as a symbolic link to the test command, and therefore supports all the options of the test command.
  • The test command can be used in conjunction with other commands, such as if, while, and until.

Related commands