Bash Shell: Test if a file or directory exists

When using bash programming, we often need to check whether the file already exists, create a new file, and insert data into the file. Sometimes we also need to execute other scripts from other scripts. This article will introduce about Bash Shell: testing whether a file or directory exists.

1. bash shell: Test whether the file exists

If we need to add some content or create a file from a script. First, make sure the file already exists. For example, one of my scripts creates a log in file/tmp/testfile.log and we need to make sure that file exists.

#!/bin/bash
 
if [ -f /tmp/testfile.log ]
then
    echo "File exists"
fi

The above statement can also be written using the test keyword, as shown below

#!/bin/bash
 
if test -f /tmp/testfile.log
then
    echo "File exists"
fi

Or we can write it in one line as shown below. This is very useful when writing shell scripts.

[ -f /tmp/testfile.log ] && echo "File exists"

Add other parts to the above command

[ -f /tmp/testfile.log ] && echo "File exists" || echo "File not exists"

2. bash shell: test whether the directory exists

Sometimes we need to Create a file in a directory, or a directory is required. We should all make sure that directory exists. For example, we now check if /tmp/mydir exists.

#!/bin/bash
 
if [ -d /tmp/mydir ]
then
    echo "Directory exists"
fi

The above statement can also be written using the test keyword, as shown below

#!/bin/bash
 
if test -d /tmp/mydir
then
    echo "Directory exists"
fi

Or we can write it in one line as shown below

[ -d /tmp/mydir ] && echo "Directory exists"

3, Bash Shell: Create file directory if not present

This is the best way to check if a file exists before creating it, otherwise you may receive an error message. This is useful when creating files or directories required by a shell script at runtime.

File:

[ ! -f /tmp/testfile.log ] && touch /tmp/testfile.log

Directory:

1    [ ! -d /tmp/mydir ] && mkdir -p /tmp/mydir

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