Whether in
sed or vi,
when using the substitution
command, a delimiter is required to separate the
search pattern from the replacement
string. The delimiter can be any character except blank or a newline (vi
seems to be more
restrictive than sed, although vim is extremely flexible). However, the usual
practice is to use the slash (/) as a delimiter (for example, s/
search
/
replacement
/).
When either the search pattern or the replacement string contains a slash, it is easier to change the delimiter character than to escape the slash. Thus, if the pattern was attempting to match Unix pathnames, which contain slashes, you could choose another character, such as a colon, as the delimiter:
s:/usr/mail:/usr2/mail:
Note that the delimiter appears three times and is required after the
replacement. Regardless of which delimiter you use, if it does appear in the
search pattern or the replacement, put a backslash (\) before it to escape it.
If you don't know what characters the search pattern might have (in a shell program that handles any kind of input, for instance), the safest choice for the delimiter can be a control character.
You can use any delimiter for a pattern address (not just a slash). Put a backslash before the first delimiter. For example, to delete all lines containing /usr/mail, using a colon (:) as the delimiter:
\:/usr/mail:d
—DD and JP