I'd like to replace a string within a variable, e.g.:
Test=Today, 12:34
I'd like to replace the "Today" within the variable Test with a Date variable I declared before.
I tried using the sed command:
sed -i -e "s/Today/$Date" '$Test'
But it would just print out an error and the file '$Test' is not known. Is using sed only possible with text files?
First, that's a syntax error.
$: Test=Today, 12:34
bash: 12:34: command not found
Put some quoting on it.
$: Test="Today, 12:34"
$: Test='Today, 12:34'
$: Test=Today,\ 12:34
Then you can just use bash's built-in parameter expansion:
$: Test='Today, 12:34'
$: Date=12.12.2000
$: Test="${Test/Today/$Date}"
$: echo "$Test"
12.12.2000, 12:34
This works for me:
Test="Today, 12:34"
Date=12.12.2000
sed 's/Today/'"$Date"'/g' <<<"$Test"
Edit: If you would like to change the variable Test, like mentioned in the comment, you need the assignment:
Test="Today, 12:34"
Date=12.12.2000
Test=$(sed 's/Today/'"$Date"'/g' <<<"$Test")
To do this you don't need to make any use of sed and can, instead, make use of the little-known, but extremely handy feature of Bash called parameter expansion described here. I only know about this because it came up in a job interview once and the interviewer shared it with me then left me to clean my brains up off the floor...
Test='Today, 12:34'
Date='12.12.2000'
echo "${Test/Today/$Date}"
---
12.12.2000, 12:34
As I said, this blew my mind in that job interview. I didn't get the job, but I've used this feature just about every day since.
for f in *.pdf; do echo "${f/%.pdf/.test}"; done. This will print each file name with the last occurrence of ".pdf" changed to ".test".It's very important to test :
input="a\b\c\d"
echo ${input}
echo "${input/\\//}"
echo "${input//\\//}"
Note that : only the last echo with '//', not '/', to begin, give us global replace !!
$Testis not a file. You can use:sed '....' <<< "$Test"or better do it in bash itself using"${Test/Today/$Date}"$Testor put it in double-quotes"$Test". If you use single quotes it will be treated as a string literal."${Test/Today/$Date}"isn't a command, it's an expression that produces a string. You need to do something with that string, like set a variable to it (Test="${Test/Today/$Date}"would replace the current value ofTestwith the modified version), print it (echo "${Test/Today/$Date}"), or something like that.