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This article explains how to use the md5sum command in Bash.

Bash md5sum command

md5sum command prints the 32 character and 128 bit checksum of a given file. This command converts the file into a hash using the MD5 algorithm; the syntax of this command is as follows.

md5sum [OPTION]... [FILEPATH]...

Let's try running a simple md5sum command on a text file with the following content:

Hello! this is md5sum command checking from jiyik.com

The file name is jiyik1; the md5sum command for this file will be:

md5sum jiyik1.txt

The above command will convert the file jiyik1.txt to md5 hash. View the result:

7a09013df4a60cc5eda609d03008c547  jiyik1.txt

We can also display this output in BSD format using the --tag option.

md5sum --tag jiyik1.txt

The output of this command will be:

MD5 (jiyik1.txt) = 7a09013df4a60cc5eda609d03008c547

There are many different options that can be used with md5sum. See the table below.

md5sumThe command can be used in different ways, including using md5 on multiple files at once, showing only modified files, and identifying invalid hashes.

Using md5sum on multiple files at once in Bash

md5sum can also be used to verify multiple files at once. Let’s create two more text files and then try to verify all three files at once.

jiyik2.txt:

Hello! this is md5sum command checking from jiyik.com file 2
jiyik3.txt:

Hello! this is md5sum command checking from jiyik.com file 3

Now the command to get the hash of multiple files at once is:

md5sum jiyik1.txt jiyik2.txt jiyik3.txt > hashes

The above command will only convert the file into hash without displaying the output. To display the output, we need to run the following command:

md5sum --check hashes

The command above will show you whether the file was successfully converted to a hash. See the output:

jiyik1.txt: OK
jiyik2.txt: OK
jiyik3.txt: OK

Display Modified Files Using md5sum in Bash

md5sumThe command can also display the modified files when applying md5sum to multiple files. First, to modify the files, use the following command:

echo "!" >> jiyik1.txt

The above command will modify the file jiyik1.txt. Now let us display the modified file using md5sum option.

See the command:

md5sum --quiet --check hashes

The above command will find the modified files and print the names in the output. See the output:

jiyik1.txt: FAILED
md5sum: WARNING: 1 computed checksum did NOT match

Identifying Invalid Hashes in Bash Using md5sum

We can also use the md5sum command with options to identify invalid files. For this, we use the -warn option and the sed command to insert extra characters to make the file invalid.

Look at the first command:

sed -i '1s/.*/a&/' hashes

The command above will add the extraction characters to the first line of the output. See the output of this command:

sed: -e expression #1, char 2: extra characters after command

Now let's check for invalid hashes using the md5sum command with the --warn option. See the command:

md5sum --warn --check hashes

The above will show the files with invalid hashes in the output. See the output:

jiyik1.txt: FAILED
jiyik2.txt: OK
jiyik3.txt: OK
md5sum: WARNING: 1 computed checksum did NOT match

Get md5sum output without filename in Bash

As we can see, md5sum returns the hash output with the file name, but sometimes we need to get the output without the file name so that we can use it further. The solution to this problem is the awk command, a domain specific language used in text processing, data extraction, and reporting tools.

Follow the points below to get output without filename in Bash:

We assign the output to a variable.

First, we run md5sum on the given file using the awk command and print $1.

See the command:

DemoMD5= md5sum jiyik1.txt | awk '{ print $1 }'

The above will only return the hash output of the md5sum output.

Output:

698ac7ad395a9c887b1abf3c9ded7abe

If you don't want to use awkthe command, there is another way where we can get the hash output directly from md5sum without the file name. We assign the md5sum output to an array and then print it.

View the command:

DemoMD5=($(md5sum jiyik1.txt))
echo $DemoMD5

The above command will also directly get the hash output md5sum without the file name. View the output:

698ac7ad395a9c887b1abf3c9ded7abe