What delimiters can you use in sed?

问题

We normally see people complaining about the unknown option to s\' error in sed when they want to use a pattern that contains the sed delimiter.

For example, if we are using /:

$ var=\"hel/lo\"
$ sed \"s/a/$var/g\" <<< \"haha\"
sed: -e expression #1, char 9: unknown option to `s\'

So we advise to use another delimiter, for example |:

$ sed \"s|a|$var|g\" <<< \"haha\"
hhel/lohhel/lo

However, I want to know what are the possible delimiters sed can accept... since it seems to be almost any character including regex-like ones (*, ?, ., ...)!

In my sed (GNU sed) 4.2.2:

$ sed \'s/a/b/g\' <<< \"haha\"
hbhb
$ sed \'s_a_b_g\' <<< \"haha\"
hbhb
$ sed \'s#a#b#g\' <<< \"haha\"
hbhb
$ sed \'s$a$b$g\' <<< \"haha\"
hbhb
$ sed \'s?a?b?g\' <<< \"haha\"
hbhb
$ sed \'s*a*b*g\' <<< \"haha\"
hbhb
$ sed \'s-a-b-g\' <<< \"haha\"
hbhb
$ sed \'s.a.b.g\' <<< \"haha\"
hbhb
$ sed \'sXaXbXg\' <<< \"haha\"
hbhb
$ sed \'sxaxbxg\' <<< \"haha\"
hbhb
$ sed \'s1a1b1g\' <<< \"haha\"
hbhb

Even a works here if it is escaped:

$ sed \'saaabag\' <<< \"haha\"
sed: -e expression #1, char 5: unknown option to `s\'
$ sed \'sa\\aabag\' <<< \"haha\"
hbhb

Is there any specification for this?

回答1:

Perhaps the closest to a standard, the POSIX/IEEE Open Group Base Specification says:

[2addr] s/BRE/replacement/flags

Substitute the replacement string for instances of the BRE in the pattern space. Any character other than backslash or newline can be used instead of a slash to delimit the BRE and the replacement. Within the BRE and the replacement, the BRE delimiter itself can be used as a literal character if it is preceded by a backslash."

来源：https://stackoverflow.com/questions/33914360/what-delimiters-can-you-use-in-sed

标签

sed

gnu

delimiter