Regex with sed to search in files - regex

I want to search recursiv in files for a given pattern and replace them. The search is for a string like "['DB']['1']['HOST'] = 'localhost'". If testing the regex the following doesn't print anything. Can't see an error in this regex? Could anyone help?
sed -n '/\[\'HOST\'\]\s?=\s?(?:\'|")(.+)(?:\'|")/p' /path/to/file

POSIX regex does not support non-capturing groups. Besides, you have not specified the -E option and the pattern is parsed as a BRE POSIX pattern where the capturing parentheses should be escaped. Also, the single quotes cannot be escaped to be used in a sed regex pattern, use \x27 instead.
Use
sed -En '/\[\x27HOST\x27\]\s?=\s?[\x27"][^\x27"]+[\x27"]/p'
See an online demo:
s="a string like ['DB']['1']['HOST'] = 'localhost'."
sed -En '/\[\x27HOST\x27\]\s?=\s?[\x27"][^\x27"]+[\x27"]/p' <<< "$s"
Besides, instead of \s, it might be a good idea to use [[:space:]].

Related

bash tool to search and replace text (while leaving text in the middle the same)

I have text files that look like this:
foo(bar(some_id)) I want to replace that with
bleh(some_id)
I can come up with the regex to find the instances, which is: foo\(bar\([a-zA-z0-9_]+\)\). But I dont know how to express that I want to keep the text in the middle the same.
Any suggestion? (I'm thinking of using sed or awk or any standard bash tool, whichever is easier )
You can use
sed -E 's/foo\(bar\(([^()]*).*/bleh(\1)/'
sed 's/foo(bar(\([^()]*\).*/bleh(\1)/'
The first pattern is POSIX ERE compliant, hence the -E option.
The foo\(bar\(([^()]*).* POSIX ERE pattern matches foo(bar(, then captures any zero or more chars other than ( and ) into Group 1 (\1 refers to this group value from the replacement pattern), and then matches the rest of string. After the replacement, the Group 1 value remains. You may add .* at the start if there is text before foo(bar(.
The second sed command is POSIX BRE equivalent of the above command.
See an online demo:
s='foo(bar(some_id))'
sed -E 's/foo\(bar\(([^()]*).*/bleh(\1)/' <<< "$s"
# => bleh(some_id)
sed 's/foo(bar(\([^()]*\).*/bleh(\1)/' <<< "$s"
# => bleh(some_id)
Using sed
$ sed 's/.*\(([^)]*)\).*/bleh\1/' input_file
bleh(some_id)

Bash script to enclose words in single quotes

I'm trying to write a bash script to enclose words contained in a file with single quotes.
Word - Hello089
Result - 'Hello089',
I tried the following regex but it doesn't work. This works in Notepad++ with find and replace. I'm not sure how to tweak it to make it work in bash scripting.
sed "s/(.+)/'$1',/g" file.txt > result.txt
Replacement backreferences (also called placeholders) are defined with \n syntax, not $n (this is perl-like backreference syntax).
Note you do not need groups here, though, since you want to wrap the whole lines with single quotation marks. This is also why you do not need the g flags, they are only necessary when you plan to find multiple matches on the same line, input string.
You can use the following POSIX BRE and ERE (the one with -E) solutions:
sed "s/..*/'&',/" file.txt > result.txt
sed -E "s/.+/'&',/" file.txt > result.txt
In the POSIX BRE (first) solution, ..* matches any char and then any 0 or more chars (thus emulating .+ common PCRE pattern). The POSIX ERE (second) solution uses .+ pattern to do the same. The & in the right-hand side is used to insert the whole match (aka \0). Certainly, you may enclose the whole match with capturing parentheses and then use \1, but that is redundant:
sed "s/\(..*\)/'\1',/" file.txt > result.txt
sed -E "s/(.+)/'\1',/" file.txt > result.txt
See the escaping, capturing parentheses in POSIX BRE must be escaped.
See the online sed demo.
s="Hello089";
sed "s/..*/'&',/" <<< "$s"
# => 'Hello089',
sed -E "s/.+/'&',/" <<< "$s"
# => 'Hello089',
$1 is expanded by the shell before sed sees it, but it's the wrong back reference anyway. You need \1. You also need to escape the parentheses that define the capture group. Because the sed script is enclosed in double quotes, you'll need to escape all the backslashes.
$ echo "Hello089" | sed "s/\\(.*\\)/'\1',/g"
'Hello089',
(I don't recall if there is a way to specify single quotes using an ASCII code instead of a literal ', which would allow you to use single quotes around the script.)

Using regex and sed to replace a string inside of a file

Having the following string inside of a text file.
{"_job":"delete","query":{"query":{"bool":{"must":[{"term":{"_id":"28381"}}],"should":[]}}},"script":{"inline":"ctx._source.meta='This
is a ' test string Peedr'"},"timestamp":1518165383,"host":"","port":"9200","index":"","docType":"","customIndexer":""}
I would like to replace all the ' that are inside the ctx._source.meta='' part with \' using sed.
In the example above I've This is a ' test string Peedr which I would like to convert to This is a \' test string Peedr, so the desired output would be:
{"_job":"delete","query":{"query":{"bool":{"must":[{"term":{"_id":"28381"}}],"should":[]}}},"script":{"inline":"ctx._source.meta='This
is a \' test string
Peedr'"},"timestamp":1518165383,"host":"","port":"9200","index":"","docType":"","customIndexer":""}
I'm using the following regex to get the ' that is inside the ctx._source.meta string (3rd capture group).
(meta=')(.*?)(')(.*?)(')
I've the regex, but I dont know how to use the sed comand in order to replace the 3rd capture group with \'.
Can someone give me a hand and tell me the sed comand I have to use?
Thanks in advance
sed generally does not support the Perl regex extensions, so the non-greedy .*? will probably not do what you hope. If you want to use Perl regex, use Perl!
perl -pe "s/(meta='.*?)(')(.*?')/\$1\\\\\$2\$3/"
This will still not necessarily work if the input is malformed; a better approach would be to specifically exclude single quotes from the match, and then you don't need the non-greedy matching.
sed "s/\\(meta='[^']*\\)'\\([^']*'\\)/\\1\\\\'\\2/"
In both cases, the number of backslashes required to escape the backslashes inside the shell's double quotes is staggering.
You put back-references to groups except one you want to replace. There is a better way to accomplish same task:
sed -E "s/(ctx\._source\.meta=')([^']*)(')([^']*')/\1\2\\'\4/"
You may use:
sed "s/ ' / \\\' /g" sample.txt
The first part will instruct sed to only look for a single quote between 2 spaces, as such ctx._source.meta='This and string Peedr'"} will not match, hence will not be changed.
Edit:
At the poster's request, I edited my sed command to apply to extra use cases:
sed "s/\(ctx._source.meta='.*\)'\(.*Peedr'\"\)/\1\\\'\2/g"

Replace some dots(.) with commas(,) with RegEx and awk or sed

I want to replace dots with commas for some but not all matches:
hostname_metric (Index: 1) to hostname;metric (avg);22.04.2015 13:40:00;3.0000;22.04.2015 02:05:00;2.0000;22.04.2015 02:00:00;650.7000;2.2594;
The outcome should look like this:
hostname_metric (Index: 1) to hostname;metric (avg);22.04.2015 13:40:00;3,0000;22.04.2015 02:05:00;2,0000;22.04.2015 02:00:00;650,7000;2,2594;
I was able to identify the RegEx which should work to find the correct dots.
;[0-9]{1,}\.[0-9]{4}
But how can I replace them with a comma with awk or sed?
Thanks in advance!
Adding some capture groups to the regex in your question, you can use this sed one-liner:
sed -r 's/(;[0-9]{1,})\.([0-9]{4})/\1,\2/g' file
This matches and captures the part before and after the . and uses them in the replacement string.
On some versions of sed, you may need to use -E instead of -r to enable Extended Regular Expressions. If your version of sed doesn't understand either switch, you can use basic regular expressions and add a few escape characters:
sed 's/\(;[0-9]\{1,\}\)\.\([0-9]\{4\}\)/\1,\2/g' file
sed 's/\(;[0-9]\+\)\.\([0-9]\{4\}\)/\1,\2/g' should do the trick.

Printing a matched regexp with sed

So I'm trying to match a regexp with any string in the middle of it and then print out just that string. The syntax is sort of like this...
sed -n 's/<title>.*</title>/"what do I put here"/p' input.file
and I just want to print out whatever .* is where I typed "what do I put here". I'm not very comfortable with sed at this point so this is likely a very simple answer and I'm having trouble finding one in any of the other questions. Thanks in advance!
Capture the pattern you want to extract within \(...\), and then you can refer to it as \1 in the replacement string:
sed -n 's/<title>\(.*\)</title>/\1/p' input.file
You can have multiple \(...\) expressions, and refer to them with \1, \2, \3, and so on.
If you have the GNU version of sed, or gsed, then you could simplify a bit:
sed -rn 's/<title>(.*)</title>/\1/p' input.file
With the -r flag, sed can use "extended regular expressions", which practically let's you write (...) instead of \(...\), + instead of \+, and other goodies.