I am taking efforts to learn sed and encounter such a situation
$ echo "abcd" | sed -n "/b/p"
abcd
it works properly,
$ echo "abcd" | sed -n "
→ /b/p"
abcd
good again, but
$ echo "Abcd" | sed -n "/b
/p"
sed: -e expression #1, char 2: unterminated address regex
What's the problem with the error report?
/b/p is a complete sed command. Each sed command needs to be on a single line. When you say /b on one line, sed treats it as a syntax error. You can try by
echo "abcd" | sed -n "/b"
and see the result. You can also try
echo "abcd" | sed -n "/b/p
> p"
and observe that after the command is completed, the next command takes effect.
sed patterns are fundamentally line-based, so it expects the second slash to be on the same line as the first one. From info sed:
Commands within a SCRIPT or SCRIPT-FILE can be separated by semicolons (';') or newlines (ASCII 10).
Most commands in Linux are fundamentally line-based, so it expects the second slash to be on the same line as the first one. In your case to work for 3rd one you can use the below
$ echo "Abcd" | sed -n "/b\
/p"
Abcd
