In a bash script, I´d like to extract a variable string from a given string. I mean, i´d like to extract the string file.txt from the string:
This is the file.txt from my folder.
I tried:
var=$(echo "This is the file.txt from my folder.")
var=echo ${var##'This'}
...
but I´d like to make it in a cleaner way, using the expr, sed or awk commands.
Thanks
Edited:
I found another way (nevertheless, the answer with the sed command is the best one for me):
var=$(echo 'This is the file.txt from my folder.')
front=$(echo 'This is the ')
back=$(echo ' from my folder.')
var=${var##$front}
var=${var%$back}
echo $var
The following solution uses sed with s/ (substitution) to remove the leading and trailing parts:
echo "This is the file.txt from my folder." | sed "s/^This is the \(.*\) from my folder.$/\1/"
Output:
file.txt
The \( and \) enclose the part which we want to keep. This is called a group. Because it's the first (and only) group which we use in this expression, it's group 1. We later reference this group inside of the replacement string with \1.
The ^ and $ signs make sure that the complete string is matched. This is only necessary for the special case that the filename contains either "from my folder." or "This is the".