Bash – How to pipe md5 hash result in shell

bashhashsumshell-scriptUbuntu

I am looking for a simple way to pipe the result of md5sum into another command. Something like this:

$echo -n 'test' | md5sum | ...

My problem is that md5sum outputs not only the hash of the string, but also an hypen, which indicates that the input came from stdin. I checked the man file and I didn't find any flags to control output.

Best Answer

You can use the command cut; it allows you to cut a certain character/byte range from every input line. Since the MD5 hash has fixed length (32 characters), you can use the option -c 1-32 to keep only the first 32 characters from the input line:

echo -n test | md5sum | cut -c 1-32

Alternatively, you can tell cut to split the line at the every space and output only the first field: (note the quotes around the space character)

echo -n test | md5sum | cut -d " " -f 1

See the cut manpage for more options.

Related Solutions

Bash Permissions – How to Change Permission of Anonymous Pipe

So far I've found the following workaround using named FIFO:

$ mkfifo -m 600 fifo
$ cat ~/.ssh/id_rsa >fifo | ssh-add fifo
Identity added: fifo (fifo)

where the option -m sets the FIFO permission.

Bash – How Does a Program Detect the End of stdin Input?

This depends on the specific system calls a process uses; read(2) on a file descriptor returns 0 on end-of-file, while stream I/O will probably use the feof(3) call. Digging around with strace may be necessary to see exactly what some higher-level function like getline(3) or specific application is doing under the hood, but most things will probably boil down to read(2) or feof(3).

The heredoc end-label is completely optional in a shell script (though is necessary if other code will follow).

Best Answer

Related Solutions

Bash Permissions – How to Change Permission of Anonymous Pipe

Bash – How Does a Program Detect the End of stdin Input?

Related Question