We have couple of scripts where we want to replace variable evaluation method from $VAR_NAME to ${VAR_NAME}
This is required so that scripts will have uniform method for variable evaluation
I am thinking of using sed for the same, I wrote sample command which looks like follows,
echo "\$VAR_NAME" | sed 's/^$[_a-zA-Z0-9]*/${&}/g'
output for the same is
${$VAR_NAME}
Now i don't want $ inside {}, how can i remove it?
Any better suggestions for accomplishing this task?
EDIT
Following command works
echo "\$VAR_NAME" | sed -r 's/\$([_a-zA-Z]+)/${\1}/g'
EDIT1
I used following command to do replacement in script file
sed -i -r 's:\$([_a-zA-Z0-9]+):${\1}:g' <ScriptName>
Since the first part of your sed command searches for the $ and VAR_NAME, the whole $VAR_NAME part will be put inside the ${} wrapper.
You could search for the $ part with a lookbehind in your regular expression, so that you end up ending the sed call with /{&}/g as the $ will be to the left of your matched expression.
http://www.regular-expressions.info/lookaround.html
http://www.perlmonks.org/?node_id=518444
I don't think sed supports this kind of regular expression, but you can make a command that begins perl -pe instead. I believe the following perl command may do what you want.
perl -p -e 's/(?<=\$)[_a-zA-Z0-9]*/{$&}/g'
PCRE Regex to SED
Related
Hi am trying to extract the part of the line after a decimal.
My input line is
A-b-2.0.2-c
I want to use sed to get the output as
2.0.2-c
Can some one help me out?
Not perfect, but working:
echo "A-b-2.0.2-c" | sed -r -n -e 's/^[^0-9]+([0-9.]+.*)$/\1/p'
The issue is that the sed command does not support non-greedy matching which is why you have to use an exclusion pattern for the leading part of the string. For a more precise matching pattern you'd have to use some other tool.
This is definetly an exercise sed is made for. With the information that you provide following would work:
$ sed 's/A-b-//' input.txt
There is also a bash way to do it:
#!/usr/bin/bash
input="A-b-2.0.2-c"
echo ${input/A-b-/}
would also extract the line after the decimal.
I am trying to change the values in a text file using sed in a Bash script with the line,
sed 's/draw($prev_number;n_)/draw($number;n_)/g' file.txt > tmp
This will be in a for loop. Why is it not working?
Variables inside ' don't get substituted in Bash. To get string substitution (or interpolation, if you're familiar with Perl) you would need to change it to use double quotes " instead of the single quotes:
# Enclose the entire expression in double quotes
$ sed "s/draw($prev_number;n_)/draw($number;n_)/g" file.txt > tmp
# Or, concatenate strings with only variables inside double quotes
# This would restrict expansion to the relevant portion
# and prevent accidental expansion for !, backticks, etc.
$ sed 's/draw('"$prev_number"';n_)/draw('"$number"';n_)/g' file.txt > tmp
# A variable cannot contain arbitrary characters
# See link in the further reading section for details
$ a='foo
bar'
$ echo 'baz' | sed 's/baz/'"$a"'/g'
sed: -e expression #1, char 9: unterminated `s' command
Further Reading:
Difference between single and double quotes in Bash
Is it possible to escape regex metacharacters reliably with sed
Using different delimiters for sed substitute command
Unless you need it in a different file you can use the -i flag to change the file in place
Variables within single quotes are not expanded, but within double quotes they are. Use double quotes in this case.
sed "s/draw($prev_number;n_)/draw($number;n_)/g" file.txt > tmp
You could also make it work with eval, but don’t do that!!
This may help:
sed "s/draw($prev_number;n_)/draw($number;n_)/g"
You can use variables like below. Like here, I wanted to replace hostname i.e., a system variable in the file. I am looking for string look.me and replacing that whole line with look.me=<system_name>
sed -i "s/.*look.me.*/look.me=`hostname`/"
You can also store your system value in another variable and can use that variable for substitution.
host_var=`hostname`
sed -i "s/.*look.me.*/look.me=$host_var/"
Input file:
look.me=demonic
Output of file (assuming my system name is prod-cfm-frontend-1-usa-central-1):
look.me=prod-cfm-frontend-1-usa-central-1
I needed to input github tags from my release within github actions. So that on release it will automatically package up and push code to artifactory.
Here is how I did it. :)
- name: Invoke build
run: |
# Gets the Tag number from the release
TAGNUMBER=$(echo $GITHUB_REF | cut -d / -f 3)
# Setups a string to be used by sed
FINDANDREPLACE='s/${GITHUBACTIONSTAG}/'$(echo $TAGNUMBER)/
# Updates the setup.cfg file within version number
sed -i $FINDANDREPLACE setup.cfg
# Installs prerequisites and pushes
pip install -r requirements-dev.txt
invoke build
Retrospectively I wish I did this in python with tests. However it was fun todo some bash.
Another variant, using printf:
SED_EXPR="$(printf -- 's/draw(%s;n_)/draw(%s;n_)/g' $prev_number $number)"
sed "${SED_EXPR}" file.txt
or in one line:
sed "$(printf -- 's/draw(%s;n_)/draw(%s;n_)/g' $prev_number $number)" file.txt
Using printf to build the replacement expression should be safe against all kinds of weird things, which is why I like this variant.
I have this
exec 5<>/dev/tcp/twitter.ca/80
echo -e "GET / HTTP/1.0\n" >&5
cat <&5
I looked a similar script
curl http://cookpad.com 2>&1 | grep -o -E 'href="([^"#]+)"' | cut -d'"' -f2
but I need to use the sed command only.
the output i get is this
sed: -e expression #1, char 2: extra characters after command
#!/bin/bash
exec 5<>/dev/tcp/twitter.ca/80
echo -e "GET / HTTP/1.0\n" >&5
cat <&5 | sed -r -e 'href="([^"#]+)"'
Is what I currently have and I guess what im trying to do is how to use sed to strip it of all extras and keep it with just the htmls?
my output should be look something like this:
href="UnixFortune.apk"
href="UnixFortune-1.0.tgz"
href="BeagleCar.apk"
href="BeagleCar.zip"
sed is a scripting language. Your command looks like you are trying to use the h command (copy pattern to hold space) with options starting with ref=... but the h command doesn't take any options.
Anyway, the command you want is the s command, which performs substitutions. Namely, you want to substitute everything before and after the matching group with nothing (and thus print only the captured group).
sed -r -e 's/.*href="([^"#]+)".*/\1/'
However, this still doesn't do the right thing if there are multiple matches on a line (or lines without a match, although that is easy to fix with sed -n 's/.../p'). You can certainly solve that in sed, but I would suggest you go with grep -o instead, unless you specifically want to learn, write, and maintain sed script. (Or, alternatively, rewrite into an Awk or Perl script. Perl in particular has a lot more leverage for tasks like this.)
And of course, for this particular task, the proper tool is an HTML parser. There is no way to properly pick apart HTML using just regular expressions. See e.g. How to extract links from a webpage using lxml, XPath and Python?
I'm trying to replace instances of {$pear_root} in a config file with the $PEAR_ROOT variable in a shell script.
Using the method from here under "A Note About Bash Escape Character" I have:
ESC_PEAR_ROOT="${PEAR_ROOT//\//\\/}"
sed -i "s/{\$pear_root}/${ESC_PEAR_ROOT}/"../.serverconfig/test.txt
I'm getting back 34: Bad substitution which I think may mean that this is unsupported.
The problem seems to be the use of s/find/replace/, as I get the same error whether doing this with sed or with perl.
What is the simplest way to do this:
APP_ROOT=$(php ./scripts/get_realpath.php '../')
PEAR_ROOT="$APP_ROOT/pear"
ESC_PEAR_ROOT="${PEAR_ROOT//\//\\/}"
sed -e "s/{\$pear_root}/${ESC_PEAR_ROOT}/"../.serverconfig/test.txt
And end up with all instances of {$pear_root} in test.txt replaced with the path from PEAR_ROOT?
I'm not attached to this method - anything reliable will do.
This is a bit silly, but I notice you're missing a space between the end of your expression and the name of the file to which you wish to apply it.
/tmp $ sed -e 's/{$pear_root}/'"$PATH"'/' test
/tmp $ sed -e 's/{$pear_root}/'"$PATH"'/'test
sed: bad option in substitution expression
Ok, solved it.
The problem was:
This:
ESC_PEAR_ROOT="${PEAR_ROOT//\//\\/}"
Should have been this:
ESC_PEAR_ROOT="{PEAR_ROOT//\//\\/}"
That was what was causing my "bad substitution" error.
Also, realized I didn't need to escape, since I could just use a different delimiter to s, so I don't even need that line.
Final result ended up as:
APP_ROOT=$(php ./scripts/get_realpath.php '../')
PEAR_ROOT="$APP_ROOT/pear"
sed -i "s#{\$pear_root}#${PEAR_ROOT}#g" ../.serverconfig/test.txt
I'm trying to write a shell script that does a search and replace inside a configuration file upon start-up.
The string we're trying to replace is:
include /etc/nginx/https.include;
and we want to replace it with a commented version:
#include /etc/nginx/https.include;
The file that contains the string that we want to replace is:
/etc/nginx/app-servers.include
I'm not a Linux guru and can't seem to find the command to do this.
perl -p -i -e 's%^(include /etc/nginx/https.include;)$%#$1%' /etc/nginx/ap-servers.include
If the line might not end in the ;, use instead:
perl -p -i -e 's%^(include /etc/nginx/https.include;.*)$%#$1%' /etc/nginx/ap-servers.include
If you want to preserve the original file, add a backup extension after -i:
perl -p -i.bak -e 's%^(include /etc/nginx/https.include;)$%#$1%' /etc/nginx/ap-servers.include
Now, explaining. The -p flag means replace in-place. All lines of the file will be fed to the expression, and the result will be used as replacement. The -i flag indicates the extension of the backup file. By using it without anything, you prevent generation of backups. The -e tells Perl to get the following parameter as an expression to be executed.
Now, the expression is s%something%other%. I use % instead of the more traditional / to avoid having to escape the slashes of the path. I use parenthesis in the expression and $1 in the substituted expression for safety -- if you change one, the other will follow. Thus, %#$1% is actually the second % of s, followed by the desired #, $1 indicating the pattern inside parenthesis, and the last % of s.
HTH. HAND.
sed -i 's/foo/bar/g' config.txt
This replaces all instances of foo (case insensitive) with bar in the file config.txt
Check out sed:
sed -i -r 's|^(include /etc/nginx/https.include;)$|#\1|' /etc/nginx/app-servers.include
-i means do the substitution in-place and -r means to use extended regular expressions.
cd pathname
for y in `ls *`;
do sed "s/ABCD/DCBA/g" $y > temp; mv temp $y;
done
This script shold replace string ABCD to DCBA in all the files in pathname