There are several things wrong (or potentially wrong) with this line:

1. Do not use "sed -i"
You shouldn't use "sed -i" for reasons stated here. Further, if you insist on using the "-i" switch of GNU sed you have to provide a file to be changed. Using "sed < file" means sed receives data via <stdin>, not from a file. sed is simply unable to change its <stdin> and even if it could - you wouldn't notice any effect. The line would have to read:

Code:

sed -i <sed-expr> file

2. Use extensive quoting
The way you intermix fixed and variable parts on the commandline you are not guaranteed to end with a single string as argument to "sed". Always enclose sed-programs in single quotes! To do what you want to do you should enclose your variables in double quotes this way:

Code:

sed '<sed-expr>'"$var1"'<rest-of-expression>' file

Applying all this to your line it should look like this (line two preserves the inode information - if you don't need that replace it by a simple "mv"):

Code:

sed 's/'"$var2"'/'"$var3"'/' file1 > outfile
cat outfile > file1 ; rm outfile

I hope this helps.

bakunin