Replace file extension in git repository

The following shell script replaces one file extension with another in a git repository.

For example, you would like to replace all .md with .markdown:

Bonuses:

What I learned while creating the above script:

Shell command to get the basename of a path basename and the path without basename dirname:

› mypath=$(pwd)
› echo $mypath
/Users/azalea/Dropbox/Projects/azalea.github.io

› basename $mypath
azalea.github.io

› dirname $mypath
/Users/azalea/Dropbox/Projects 

And use Shell parameter expansion to get file extension and file name without extension:

› name=$(basename $mypath)
› echo $name
azalea.github.io

› extension="${name##*.}"
› echo $extension
io

› name_wo_ext="${name%.*}"
› echo $name_wo_ext
azalea.github

Explanation of ${name##*.}:

${parameter##word}: if the beginning of the parameter matches the pattern specified by word, the longest matching pattern is deleted from parameter. So in ${name##*.}, when name=”azalea.github.io”, the longest matching pattern of “*.” from the beginning of $name is “azalea.gitgub.”, which is deleted, leaving “io”.

Explanation of ${name%.*}:

${parameter%word}: if the end of the parameter matches the pattern specified by word, the shortest matching pattern is deleted from parameter. So in ${name%.*}, when name=”azalea.github.io”, the shortest matching pattern of “.*” from the end of $name is “.io”, which is deleted, leaving “azalea.github”.

Quizzes

Q: How to get “azalea” out of “azalea.github.io”.

A:

› echo ${name%%.*}
azalea

Q: Use parameter expansion to achieve the function of basename:

A:

› echo ${mypath##*/}
azalea.github.io