I am using sed in a shell script to edit filesystem path names. Suppose I want to replace
/foo/bar
with
/baz/qux
However, sed's s/// command uses the forward slash / as the delimiter. If I do that, I see an error message emitted, like:
▶ sed 's//foo/bar//baz/qux//' FILE
sed: 1: "s//foo/bar//baz/qux//": bad flag in substitute command: 'b'
Similarly, sometimes I want to select line ranges, such as the lines between a pattern foo/bar and baz/qux. Again, I can't do this:
▶ sed '/foo/bar/,/baz/qux/d' FILE
sed: 1: "/foo/bar/,/baz/qux/d": undefined label 'ar/,/baz/qux/d'
What can I do?
You can use an alternative regex delimiter as a search pattern by backslashing it:
sed '\,some/path,d'
And just use it as is for the s command:
sed 's,some/path,other/path,'
You probably want to protect other metacharacters, though; this is a good place to use Perl and quotemeta, or equivalents in other scripting languages.
From man sed:
/regexp/
Match lines matching the regular expression regexp.
\cregexpc
Match lines matching the regular expression regexp. The c may be any character other than backslash or newline.
s/regular expression/replacement/flags
Substitute the replacement string for the first instance of the regular expression in the pattern space. Any character other than backslash or newline can be used instead of a slash to delimit the RE and the replacement. Within the RE and the replacement, the RE delimiter itself can be used as a literal character if it is preceded by a backslash.
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."
When there is a slash / in theoriginal-string or the replacement-string, we need to escape it using \. The following command is work in ubuntu 16.04(sed 4.2.2).
sed 's/\/foo\/bar/\/baz\/qux/' file
Related
I am using sed in a shell script to edit filesystem path names. Suppose I want to replace
/foo/bar
with
/baz/qux
However, sed's s/// command uses the forward slash / as the delimiter. If I do that, I see an error message emitted, like:
▶ sed 's//foo/bar//baz/qux//' FILE
sed: 1: "s//foo/bar//baz/qux//": bad flag in substitute command: 'b'
Similarly, sometimes I want to select line ranges, such as the lines between a pattern foo/bar and baz/qux. Again, I can't do this:
▶ sed '/foo/bar/,/baz/qux/d' FILE
sed: 1: "/foo/bar/,/baz/qux/d": undefined label 'ar/,/baz/qux/d'
What can I do?
You can use an alternative regex delimiter as a search pattern by backslashing it:
sed '\,some/path,d'
And just use it as is for the s command:
sed 's,some/path,other/path,'
You probably want to protect other metacharacters, though; this is a good place to use Perl and quotemeta, or equivalents in other scripting languages.
From man sed:
/regexp/
Match lines matching the regular expression regexp.
\cregexpc
Match lines matching the regular expression regexp. The c may be any character other than backslash or newline.
s/regular expression/replacement/flags
Substitute the replacement string for the first instance of the regular expression in the pattern space. Any character other than backslash or newline can be used instead of a slash to delimit the RE and the replacement. Within the RE and the replacement, the RE delimiter itself can be used as a literal character if it is preceded by a backslash.
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."
When there is a slash / in theoriginal-string or the replacement-string, we need to escape it using \. The following command is work in ubuntu 16.04(sed 4.2.2).
sed 's/\/foo\/bar/\/baz\/qux/' file
I am using sed in a shell script to edit filesystem path names. Suppose I want to replace
/foo/bar
with
/baz/qux
However, sed's s/// command uses the forward slash / as the delimiter. If I do that, I see an error message emitted, like:
▶ sed 's//foo/bar//baz/qux//' FILE
sed: 1: "s//foo/bar//baz/qux//": bad flag in substitute command: 'b'
Similarly, sometimes I want to select line ranges, such as the lines between a pattern foo/bar and baz/qux. Again, I can't do this:
▶ sed '/foo/bar/,/baz/qux/d' FILE
sed: 1: "/foo/bar/,/baz/qux/d": undefined label 'ar/,/baz/qux/d'
What can I do?
You can use an alternative regex delimiter as a search pattern by backslashing it:
sed '\,some/path,d'
And just use it as is for the s command:
sed 's,some/path,other/path,'
You probably want to protect other metacharacters, though; this is a good place to use Perl and quotemeta, or equivalents in other scripting languages.
From man sed:
/regexp/
Match lines matching the regular expression regexp.
\cregexpc
Match lines matching the regular expression regexp. The c may be any character other than backslash or newline.
s/regular expression/replacement/flags
Substitute the replacement string for the first instance of the regular expression in the pattern space. Any character other than backslash or newline can be used instead of a slash to delimit the RE and the replacement. Within the RE and the replacement, the RE delimiter itself can be used as a literal character if it is preceded by a backslash.
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."
When there is a slash / in theoriginal-string or the replacement-string, we need to escape it using \. The following command is work in ubuntu 16.04(sed 4.2.2).
sed 's/\/foo\/bar/\/baz\/qux/' file
I'm trying to replace some regex line in a apache file.
i define:
OLD1="[0-9]*.[0-9]+"
NEW1="[a-z]*.[0-9]"
when i'm executing:
sed -i 's/$OLD1/$NEW1/g' demo.conf
there's no change.
This is what i tried to do
sed -i "s/${OLD1}/${NEW1}/g" 001-kms.conf
sed -i "s/"$OLD1"/"$NEW1"/g" 001-kms.conf
sed -i "s~${OLD1}~${NEW1}~g" 001-kms.conf
i'm expecting that the new file will replace $OLD1 with $NEW1
OLD1="[0-9]*.[0-9]+"
Because the [ * . are all characters with special meaning in sed, we need to escape them. For such simple case something like this could work:
OLD2=$(<<<"$OLD1" sed 's/[][\*\.]/\\&/g')
It will set OLD2 to \[0-9\]\*\.\[0-9\]+. Note that it doesn't handle all the possible cases, like OLD1='\.\[' will convert to OLD2='\\.\\[ which means something different. Implementing a proper regex to properly escape, well, other regex I leave as an exercise to others.
Now you can:
sed "s/$OLD2/$NEW1/g"
Tested with:
OLD1="[0-9]*.[0-9]+"
NEW1="[a-z]*.[0-9]"
sed "s/$(sed 's/[][\*\.]/\\&/g' <<<"$OLD1")/$NEW1/g" <<<'XYZ="[0-9]*.[0-9]+"'
will output:
XYZ="[a-z]*.[0-9]"
you need matching on exact string
You would need something that can match on exact string [0-9]*.[0-9]+ which sed does not support well.
Therefore instead I am using this pipeline replacing one character at a time (it also is easier to read I think):echo "[0-9]*.[0-9]+" | sed 's/0/a/' | sed 's/9/z/' | sed 's/+//'
You would have to cat your files or use find with execute to then apply this pipe.
I had tried following (from other SO answers):
- sed 's/\<exact_string/>/replacement/'doesn't work as \< and \> are left and right word boundaries respectively.
- sed 's/(CB)?exact_string/replacement/'found in one answer but nowhere in documentation
I used Win 10 bash, git bash, and online Linux tools with the same results.
when I thought matching was on the pattern rather than exact string
Replacement cannot be a regex - at most it can reference parts of the regex expression which matched. From man sed:
s/regexp/replacement/
Attempt to match regexp against the pattern space. If successful, replace that portion matched with replacement. The replacement may contain the special character & to refer to that portion of the pattern space which matched, and the special escapes \1 through \9 to refer to the corresponding matching sub-expressions in the regexp.
Additionally you have to escape some characters in your regex (specifically . and +) unless you add option -E for extended regex as per comment under your question. (N.B. only if you want to match on the full-stop . rather than it meaning any character)
$ echo "01.234--ZZZ" | sed 's/[0-9]*\.[0-9]\+/REPLACEMENT/g'
REPLACEMENT--ZZZ
This question already has answers here:
How to insert strings containing slashes with sed? [duplicate]
(11 answers)
Closed 6 years ago.
I am trying to replace a script call with a script call from a sub directory.
For example, originally I had ./output.sh in my script to call the output.sh script in the current directory.
I want to replace ./output.sh with ../output.sh so that it calls output.sh in the parent directory.
I tried
sed -i -e 's/../\output.sh/./\output.sh/g' scriptName.sh
This returns with
char 17: unknown option to 's'
Any help with the sed escape character syntax would be great.
Sed is bad at this; you'll risk turning an already existing ../output.sh into .../output.sh if you're not careful.
This is the best sed can do:
sed -i 's#output\.sh#../$#g' scriptName.sh
(I'm using # in place of / so that there are no forward slashes to escape. Sed accepts any punctuation character in place of forward slash.)
Note that this will convert ../output.sh to ../../output.sh but at least it doesn't create that triple-dot error.
Instead, try perl:
perl -pie 's#(?<!\.\./)(output\.sh\b)#../$1#g' scriptName.sh
This uses a negative look-behind to ensure it doesn't traverse to the parent's parent. It also allows using \b to denote a word break just in case you have something like output.shelf somewhere.
This would do the trick. Substitutes every appearance of ./output.sh for ../output.sh :
sed 's/\.\/output\.sh/\.\.\/output\.sh/g' scriptName.sh
The escape character is \. You should use it to escape:
Every dot .. The dot is used as any character in regex.
Every slash /. The slash character is used as delimiter between regex on the scommand.
The slash character is special in sed's s command if you formulate it as s/something/replacement/flags, so the slashes in your file paths cause the error. Fortunately, you can use any other character right after s, for example s#something#replacement#flags. So, replacing the command with s#\./output.sh#../output.sh#g should do the trick.
Note two additional changes: you have to escape the dot in first expression since it's also a special character in regex and you also got reversed order of search expression and replacement (thanks charli for noticing this). You don't need the backslashes before o characters, either.
Alternatively, you can use / after s but escape the literal slashes you want to replace by preceding them with backslashes: s/\.\/output.sh/..\/\output.sh/g. It seems in your code you tried to use this solution but put the backslashes after instead of before the slashes.
i am totally new to sed and as part of script writing i am trying to replace specific string from a fiel. I know the special characters need to be escaped using backslash but the problem is if the special character is first in the line then it is not replaced....
For e.g my file contains
sldgfkls $bdxcv sldflksd
Now if i write the below code
sed -i 's/\b\$bdxcv\b/abcd/' filename
Then the above word is not replaced....But if the file contains
sldgfkls a$bdxcv sldflksd
Now if i write the below code
sed -i 's/\ba\$bdxcv\b/abcd/' filename
Then the above word is replaced.....
Please Help me here....
Clearly, \b does not consider a dollar sign to be a word character, so there is no word boundary for it to match between space and $.
Perhaps you want this instead:
sed -i 's/\(^\|[\t ]\)\$bdxcv\b/\1abcd/' filename
Assuming yours is GNU sed, see https://www.gnu.org/software/sed/manual/sed.html which contains this definition:
A “word” character is any letter or digit or the underscore character.
and thus not dollar sign.
sed cannot operator on strings, only regular expressions. Trying to figure out which characters need to be escaped to disable their regexp (or sed delimiter or sed backreference) meaning to make a regexp in sed behave as if it were a string is a fool's errand, just use a tool that can operate on strings, e.g. awk.
$ awk '{for (i=1;i<NF;i++) if ($i == "$bdxcv") $i="abcd"} 1' file
sldgfkls abcd sldflks
The above uses string comparison and string assignment - no need to escape anything unless one of the strings contained the string delimiter, ".