Hello fellow ladies and gentlemen, I haven't been doing this long, and here is my trouble:

First, I have a text file called songinfo, inside is listed song information in this format (one song per line):

song_name:album_name:artist_name:song_length:year

Next, I have a script that is eventually supposed to allow the user to modify any field in a song entry. This is after having isolated the song's line in the file. The next part could so far be summarized like:
_____________________________________________________

echo "Choose which attribute to edit: "
echo "A -- song name"
echo "B -- album name"
echo "C -- artist name"
echo "D -- year"
echo
echo "Edit option: "
read change

case $change in
a|A)
oldsong=`cut -f 1 -d :`
echo -n "Enter new song name: "
read newsong
sed w s/$oldsong/$newsong/ songinfo
;;
b|B)
oldalbum=`cut -f 2 -d :`
echo -n "Enter new album name: "
read newalbum
sed w s/$oldalbum/$newalbum/ songinfo
;;
...and so on
___________________________________________________

My question is how do I properly user sed to replace the field in the songinfo from the old value to the new value? I don't know if I'm misusing sed, or the variables even.

As of now, the output is that there is no visible change after execution, and if I check the songinfo file, the text will now have changed.

Please and thanks in advance

"man sed" - check the "-i" to allow edit in-place (i.e. in the file).
Not that I'd normally recommend that - backups might be an idea...

This amounts to an inventory application.

You say "I have a text file." Do you mean the file already exists, or you contemplate creating it? The layout of the data will be a factor in the complexity of your program.

Suggestion: consider the merits of having not one file, but four:
File A for song name
File B for album name
File C for artist name
File D for year

Data for each song would occupy the same line in each of the four files. This multi-file approach could be advantageous if you need to extend the content of your inventory. Suppose you wanted to add fields such as "genre" and "copyright owner." That could be easy: just create a new file, equal in length to the four existing files, with something like "-no data-" in each line.

Daniel B. Martin

Firstly, please use [code][/code] tags when displaying code or data to make it easier to read.

As others have already answered the sed question, I thought I might make some suggestions:

1. Have a look at the select function for bash as it already performs your echo / read / case portion of your script.

2. Your questions appear to be singular, "Enter new song name: ", yet your cut does not provide the ability to choose a particular line or song. So how do you know you will change the correct one?

Hope some of that helps or gives you some ideas

what if you have a line like:and you only want to change "B -- album name"

Thanks everyone, I have taken some of the aforementioned advice and it's working out better