How to read output of sed into a variable.

Question

I have variable which has value "abcd.txt".

I want to store everything before the ".txt" in a second variable, replacing the ".txt" with ".log"

I have no problem echoing the desired value:

a="abcd.txt"

echo $a | sed 's/.txt/.log/'

But how do I get the value "abcd.log" into the second variable?

Thanks,

Roger

Answer 1

You can use command substitution as:

new_filename=$(echo "$a" | sed 's/.txt/.log/')

or the less recommended backtick way:

new_filename=`echo "$a" | sed 's/.txt/.log/'`

Answer 2

You can use backticks to assign the output of a command to a variable:

logfile=`echo $a | sed 's/.txt/.log/'`

That's assuming you're using Bash.

Alternatively, for this particular problem Bash has pattern matching constructs itself:

stem=$(textfile%%.txt)
logfile=$(stem).log

or

logfile=$(textfile/%.txt/.log)

The % in the last example will ensure only the last .txt is replaced.

Answer 3

if you have Bash/ksh

$ var="abcd.txt"
$ echo ${var%.txt}.log
abcd.log
$ variable=${var%.txt}.log