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bashshellshcutgnu-coreutils

How can I remove the extension of a filename in a shell script?

What's wrong with the following code?

name='$filename | cut -f1 -d'.''

As is, I get the literal string $filename | cut -f1 -d'.', but if I remove the quotes I don't get anything. Meanwhile, typing

"test.exe" | cut -f1 -d'.'

in a shell gives me the output I want, test. I already know $filename has been assigned the right value. What I want to do is assign to a variable the filename without the extension.

Solution

  • You should be using the command substitution syntax $(command) when you want to execute a command in script/command.

    So your line would be 

    name=$(echo "$filename" | cut -f 1 -d '.')

    Code explanation:

    1. echo get the value of the variable $filename and send it to standard output
    2. We then grab the output and pipe it to the cut command
    3. The cut will use the . as delimiter (also known as separator) for cutting the string into segments and by -f we select which segment we want to have in output
    4. Then the $() command substitution will get the output and return its value
    5. The returned value will be assigned to the variable named name

    Note that this gives the portion of the variable up to the first period .:

    $ filename=hello.world
$ echo "$filename" | cut -f 1 -d '.'
hello
$ filename=hello.hello.hello
$ echo "$filename" | cut -f 1 -d '.'
hello
$ filename=hello
$ echo "$filename" | cut -f 1 -d '.'
hello