Sed
From Linuxintro
sed is a command to edit a text stream in batch mode.
For example,
sed "s/a/o/"
Will read your input (stream) from the keyboard and substitute every a by an o.
Usecases
- Remove leading white space
sed 's/^[ \t]*//'
- Replace strings
# echo "hello world" | sed "s/world/moon/" hello moon
- Insert a line a beginning of file
sed -i '1i <This is now at the first line>' <filename>
- Replace several newlines by one
sed 's/\ \{1,\}/\ /g'
- change the protocol for a given port in /etc/services:
sed -ri "s/.{16}3200/sapdp00 3200/" /etc/services
Limitations
You cannot use sed to delete linebreaks, for this you must use tr.
