How to check if a file or directory exists in Bash

Many times, when writing a Shell script, you need to perform operations based on whether the file exists. So how to check if the file exists? The following article will show you how to use the test command to check whether a file or directory exists in Bash. I hope it will be helpful to you.

test command

In Bash, you can use the test command to check whether a file exists and determine whether the file exists type.

The test command takes one of the following syntax forms:

test EXPRESSION
[ EXPRESSION ]
[[ EXPRESSION ]]

If you want your script to be portable, you should prefer using the old test [ command which is available on all POSIX shells. A new upgraded version of the test command [[ (double brackets) is supported on most modern systems using bash, zsh, and ksh as the default shell.

File operators of the test command

The test command includes the following File operators, allowing testing of specific types of files:

●　-b FILE: True if FILE exists and is a block special file.

●　-c FILE: True if FILE exists and is a special character file.

●　-d FILE: True if FILE exists and is a directory.

●　-e FILE: True if FILE exists and is a file, regardless of type (node, directory, socket, etc.).

●　-f FILE: True if FILE exists and is a regular file (not a directory or device).

●　-G FILE: True if FILE exists and has the same group as the user running the command.

●　-h FILE: True if FILE exists and is a symbolic link.

●　-g FILE: True if FILE exists and the set-group-id (sgid) flag is set.

●　-k FILE: True if FILE exists and the sticky bit flag is set.

●　-L FILE: True if FILE exists and is a symbolic link.

●　-O FILE: True if FILE exists and is owned by the user running the command.

●　-p FILE: True if FILE exists and is a pipe.

●　-r FILE: True if FILE exists and is readable.

●　-S FILE: True if FILE exists and is a socket.

●　-s FILE: True if FILE exists and has a non-zero size.

●　-u FILE: True if exists and set-user-id (suid) flags are set.

●　-w FILE: True if FILE exists and is writable.

●　-x FILE: True if FILE exists and is executable.

How to check if a file exists?

When checking whether a file exists, the most commonly used FILE operators are -e and -f. The first operator will check if the file exists regardless of file type; the second operator will only return true if the file is a regular file (not a directory or device).

When checking whether a file exists, the most readable option is to use the test command in combination with an if statement. Any of the following code snippets will check if the /etc/resolv.conf file exists:

FILE=/etc/resolv.conf
if test -f "$FILE"; then
    echo "$FILE exist"
fi

FILE=/etc/resolv.conf
if [ -f "$FILE" ]; then
    echo "$FILE exist"
fi

FILE=/etc/resolv.conf
if [[ -f "$FILE" ]]; then
    echo "$FILE exist"
fi

If you want to perform different actions based on whether the file exists, just use an if/then structure:

FILE=/etc/resolv.conf
if [ -f "$FILE" ]; then
    echo "$FILE exist"
else 
    echo "$FILE does not exist"
fi

Note: Always use double quotes to avoid problems when working with files that contain spaces in their names.

You can also use the test command without an if statement. The command after the && operator will only be executed if the exit status of the test command is true.

test -f /etc/resolv.conf && echo "$FILE exist"

[ -f /etc/resolv.conf ] && echo "$FILE exist"

[[ -f /etc/resolv.conf ] && echo "$FILE exist"

If you want to run a series of commands after the && operator, just enclose the commands with ";" Or in curly brackets separated by "&&".

[ -f /etc/resolv.conf ] && { echo "$FILE exist"; cp "$FILE" /tmp/; }

Contrary to &, the statement following the || operator is only executed when the exit status of the test command is false.

[ -f /etc/resolv.conf ] && echo "$FILE exist" || echo "$FILE does not exist"

How to check if a directory exists?

-d operator allows testing whether a file is a directory.

For example, to check whether the /etc/docker directory exists, you need to use:

FILE=/etc/docker
if [ -d "$FILE" ]; then
    echo "$FILE is a directory"
fi

[ -d /etc/docker ] && echo "$FILE is a directory"

Similarly, you can also use double brackets [[ instead of a single bracket [.

How to check if a file does not exist?

Similar to many other languages, it can be used! (exclamation point) logical NOT operator to negate the test expression:

FILE=/etc/docker
if [ ! -f "$FILE" ]; then
    echo "$FILE exist and it is a directory"
fi

Same as above:

[ ! -f /etc/docker ] || echo "$FILE does not exist"

How to check if multiple files exist?

If multiple files exist, you can use -a (or &&with[]) to test instead of using complex nested if/else constructs:

FILE=/etc/docker
if [ -f /etc/resolv.conf -a -f /etc/hosts ]; then
    echo "$FILE is a directory"
fi

FILE=/etc/docker
if [ -f /etc/resolv.conf && -f /etc/hosts ]; then
    echo "$FILE is a directory"
fi

Equivalent variant without IF statement:

[ -f /etc/resolv.conf -a -f /etc/hosts ] && echo "both files exist"

[[ -f /etc/resolv.conf && -f /etc/hosts ]] && echo "both files exist"

Recommended related video tutorials: "Linux Tutorial"

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