I would like to edit the /etc/environment file to change the MY_VARIABLE from VALUE_01 to VALUE_02.
Here is the context of the /etc/environment file:
PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin"
JAVA_HOME="/usr/java/jdk8/jdk1.8.0_92-1"
MY_VARIABLE=VALUE_01
Ideally I would like to use sed command to edit it, for example (please note it is not working command):
sed -e 'MY_VARIABLE=VALUE_02' -i /etc/environment
How can I achieve it?
sed -- 's/MY_VARIABLE=.*/MY_VARIABLE=VALUE_02/' /etc/environment
Once you check it works, add the -i option:
sed -i -- 's/MY_VARIABLE=.*/MY_VARIABLE=VALUE_02/' /etc/environment
You will probably need root access.
Instead of trying to use sed -i and hoping your version of sed implements that option and working out if it takes a mandatory argument or not (I have a feeling you're not using GNU sed like the linux tag suggests you should be), just use ed to edit files in scripts.
ed -s /etc/environment <<EOF
/^MY_VARIABLE=/c
MY_VARIABLE=VALUE_02
.
w
EOF
changes the first line starting with MY_VARIABLE= to the given new text, and writes the file back to disk.
What's the simplest way to do a find and replace for a given input string, say abc, and replace with another string, say XYZ in file /tmp/file.txt?
I am writting an app and using IronPython to execute commands through SSH — but I don't know Unix that well and don't know what to look for.
I have heard that Bash, apart from being a command line interface, can be a very powerful scripting language. So, if this is true, I assume you can perform actions like these.
Can I do it with bash, and what's the simplest (one line) script to achieve my goal?
The easiest way is to use sed (or perl):
sed -i -e 's/abc/XYZ/g' /tmp/file.txt
Which will invoke sed to do an in-place edit due to the -i option. This can be called from bash.
If you really really want to use just bash, then the following can work:
while IFS='' read -r a; do
echo "${a//abc/XYZ}"
done < /tmp/file.txt > /tmp/file.txt.t
mv /tmp/file.txt{.t,}
This loops over each line, doing a substitution, and writing to a temporary file (don't want to clobber the input). The move at the end just moves temporary to the original name. (For robustness and security, the temporary file name should not be static or predictable, but let's not go there.)
For Mac users:
sed -i '' 's/abc/XYZ/g' /tmp/file.txt
(See the comment below why)
File manipulation isn't normally done by Bash, but by programs invoked by Bash, e.g.:
perl -pi -e 's/abc/XYZ/g' /tmp/file.txt
The -i flag tells it to do an in-place replacement.
See man perlrun for more details, including how to take a backup of the original file.
I was surprised when I stumbled over this...
There is a replace command which ships with the "mysql-server" package, so if you have installed it try it out:
# replace string abc to XYZ in files
replace "abc" "XYZ" -- file.txt file2.txt file3.txt
# or pipe an echo to replace
echo "abcdef" |replace "abc" "XYZ"
See man replace for more on this.
This is an old post but for anyone wanting to use variables as #centurian said the single quotes mean nothing will be expanded.
A simple way to get variables in is to do string concatenation since this is done by juxtaposition in bash the following should work:
sed -i -e "s/$var1/$var2/g" /tmp/file.txt
Bash, like other shells, is just a tool for coordinating other commands. Typically you would try to use standard UNIX commands, but you can of course use Bash to invoke anything, including your own compiled programs, other shell scripts, Python and Perl scripts etc.
In this case, there are a couple of ways to do it.
If you want to read a file, and write it to another file, doing search/replace as you go, use sed:
sed 's/abc/XYZ/g' <infile >outfile
If you want to edit the file in place (as if opening the file in an editor, editing it, then saving it) supply instructions to the line editor 'ex'
echo "%s/abc/XYZ/g
w
q
" | ex file
Example is like vi without the fullscreen mode. You can give it the same commands you would at vi's : prompt.
I found this thread among others and I agree it contains the most complete answers so I'm adding mine too:
sed and ed are so useful...by hand.
Look at this code from #Johnny:
sed -i -e 's/abc/XYZ/g' /tmp/file.txt
When my restriction is to use it in a shell script, no variable can be used inside in place of "abc" or "XYZ". The BashFAQ seems to agree with what I understand at least. So, I can't use:
x='abc'
y='XYZ'
sed -i -e 's/$x/$y/g' /tmp/file.txt
#or,
sed -i -e "s/$x/$y/g" /tmp/file.txt
but, what can we do? As, #Johnny said use a while read... but, unfortunately that's not the end of the story. The following worked well with me:
#edit user's virtual domain
result=
#if nullglob is set then, unset it temporarily
is_nullglob=$( shopt -s | egrep -i '*nullglob' )
if [[ is_nullglob ]]; then
shopt -u nullglob
fi
while IFS= read -r line; do
line="${line//'<servername>'/$server}"
line="${line//'<serveralias>'/$alias}"
line="${line//'<user>'/$user}"
line="${line//'<group>'/$group}"
result="$result""$line"'\n'
done < $tmp
echo -e $result > $tmp
#if nullglob was set then, re-enable it
if [[ is_nullglob ]]; then
shopt -s nullglob
fi
#move user's virtual domain to Apache 2 domain directory
......
As one can see if nullglob is set then, it behaves strangely when there is a string containing a * as in:
<VirtualHost *:80>
ServerName www.example.com
which becomes
<VirtualHost ServerName www.example.com
there is no ending angle bracket and Apache2 can't even load.
This kind of parsing should be slower than one-hit search and replace but, as you already saw, there are four variables for four different search patterns working out of one parse cycle.
The most suitable solution I can think of with the given assumptions of the problem.
You can use sed:
sed -i 's/abc/XYZ/gi' /tmp/file.txt
You can use find and sed if you don't know your filename:
find ./ -type f -exec sed -i 's/abc/XYZ/gi' {} \;
Find and replace in all Python files:
find ./ -iname "*.py" -type f -exec sed -i 's/abc/XYZ/gi' {} \;
Be careful if you replace URLs with "/" character.
An example of how to do it:
sed -i "s%http://domain.com%http://www.domain.com/folder/%g" "test.txt"
Extracted from: http://www.sysadmit.com/2015/07/linux-reemplazar-texto-en-archivos-con-sed.html
If the file you are working on is not so big, and temporarily storing it in a variable is no problem, then you can use Bash string substitution on the whole file at once - there's no need to go over it line by line:
file_contents=$(</tmp/file.txt)
echo "${file_contents//abc/XYZ}" > /tmp/file.txt
The whole file contents will be treated as one long string, including linebreaks.
XYZ can be a variable eg $replacement, and one advantage of not using sed here is that you need not be concerned that the search or replace string might contain the sed pattern delimiter character (usually, but not necessarily, /). A disadvantage is not being able to use regular expressions or any of sed's more sophisticated operations.
You may also use the ed command to do in-file search and replace:
# delete all lines matching foobar
ed -s test.txt <<< $'g/foobar/d\nw'
See more in "Editing files via scripts with ed".
To edit text in the file non-interactively, you need in-place text editor such as vim.
Here is simple example how to use it from the command line:
vim -esnc '%s/foo/bar/g|:wq' file.txt
This is equivalent to #slim answer of ex editor which is basically the same thing.
Here are few ex practical examples.
Replacing text foo with bar in the file:
ex -s +%s/foo/bar/ge -cwq file.txt
Removing trailing whitespaces for multiple files:
ex +'bufdo!%s/\s\+$//e' -cxa *.txt
Troubleshooting (when terminal is stuck):
Add -V1 param to show verbose messages.
Force quit by: -cwq!.
See also:
How to edit files non-interactively (e.g. in pipeline)? at Vi SE
Try the following shell command:
find ./ -type f -name "file*.txt" | xargs sed -i -e 's/abc/xyz/g'
You can use python within the bash script too. I didn't have much success with some of the top answers here, and found this to work without the need for loops:
#!/bin/bash
python
filetosearch = '/home/ubuntu/ip_table.txt'
texttoreplace = 'tcp443'
texttoinsert = 'udp1194'
s = open(filetosearch).read()
s = s.replace(texttoreplace, texttoinsert)
f = open(filetosearch, 'w')
f.write(s)
f.close()
quit()
Simplest way to replace multiple text in a file using sed command
Command -
sed -i 's#a/b/c#D/E#g;s#/x/y/z#D:/X#g;' filename
In the above command s#a/b/c#D/E#g where I am replacing a/b/c with D/E and then after the ; we again doing the same thing
You can use rpl command. For example you want to change domain name in whole php project.
rpl -ivRpd -x'.php' 'old.domain.name' 'new.domain.name' ./path_to_your_project_folder/
This is not clear bash of cause, but it's a very quick and usefull. :)
For MAC users in case you don't read the comments :)
As mentioned by #Austin, if you get the Invalid command code error
For the in-place replacements BSD sed requires a file extension after the -i flag to save to a backup file with given extension.
sed -i '.bak' 's/find/replace' /file.txt
You can use '' empty string if you want to skip backup.
sed -i '' 's/find/replace' /file.txt
All merit to #Austin
Open file using vim editor. In command mode
:%s/abc/xyz/g
This is the simplest
In case of doing changes in multiple files together we can do in a single line as:-
user_name='whoami'
for file in file1.txt file2.txt file3.txt; do sed -i -e 's/default_user/${user_name}/g' $file; done
Added if in case could be useful.
I'm writing a bash script to non-interactively enable hibernation on a linux system. To this end, I need to insert a shell variable that contains slashes on a specific line of a while, inside quotes that are on that line.
The relevant part of the file to b edited looks like this:
GRUB_DEFAULT=0
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR="Manjaro"
GRUB_CMDLINE_LINUX_DEFAULT="quiet"
GRUB_CMDLINE_LINUX=""
I need to change it to this:
GRUB_DEFAULT=0
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR="Manjaro"
GRUB_CMDLINE_LINUX_DEFAULT="quiet resume=/dev/disk/by-partuuid/c5a552c2-fe8f-423a-9037-c35bf090d9c3"
GRUB_CMDLINE_LINUX=""
The added parameter is provided by a shell variable.
I tried this:
sed -i '\*^GRUB_CMDLINE_LINUX_DEFAULT* s*"$* '"$(grub_resume_boot_option)"'"*' /etc/default/grub
Logic that I was aiming for was: "Look for a line that starts with pattern "GRUB_CMDLINE_LINUX_DEFAULT", and replace the last " with the given pattern. Use * as delimiter to preserve the slashes in the expanded variable."
However, the command fails if there are any spaces at the end of the line. Is there any way to make it not take spaces at the end of the line into account?
Also, if there is more simple or readable solution to this, I would be very interested.
You can do:
sed -i 's#^\(GRUB_CMDLINE_LINUX_DEFAULT="quiet\)"$#\1 resume=/dev/disk/by-partuuid/c5a552c2-fe8f-423a-9037-c35bf090d9c3"#' /etc/default/grub
Example:
$ sed 's#^\(GRUB_CMDLINE_LINUX_DEFAULT="quiet\)"$#\1 resume=/dev/disk/by-partuuid/c5a552c2-fe8f-423a-9037-c35bf090d9c3"#' <<<'GRUB_CMDLINE_LINUX_DEFAULT="quiet"'
GRUB_CMDLINE_LINUX_DEFAULT="quiet resume=/dev/disk/by-partuuid/c5a552c2-fe8f-423a-9037-c35bf090d9c3"
From: https://serverfault.com/questions/885684/editing-the-value-of-grub-cmdline-linux-default-thru-bash-script
sed -i 's/^GRUB_CMDLINE_LINUX_DEFAULT="/&newstuff /' /etc/default/grub
This will add "newstuff" to the beginning of the list of params. Examples:
sed 's/^GRUB_CMDLINE_LINUX_DEFAULT="/&newstuff /' <<< 'GRUB_CMDLINE_LINUX_DEFAULT="quiet"'
GRUB_CMDLINE_LINUX_DEFAULT="newstuff quiet"
sed 's/^GRUB_CMDLINE_LINUX_DEFAULT="/&newstuff /' <<< 'GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"'
GRUB_CMDLINE_LINUX_DEFAULT="newstuff quiet splash"
sed -i "s/GRUB_CMDLINE_LINUX_DEFAULT="[^"]*/& $(grub_resume_boot_option)/" /etc/default/grub
I have to implement an application in shell programming (Unix/Linux).
I have to search a word from a text file and replace that word with my given word. I have a knowledge on shell and still learning.
I am not expecting source code. Can anybody help me or suggest me or give me some similar solution....
cat abc.txt | grep "pattern" | sed 's/"pattern"/"new pattern"/g'
The above command should work
Thanks,
Regards,
Dheeraj Rampally
Say you are looking for pattern in a file (input.txt) and want to replace it with "new pattern" in another (output.txt)
Here is the main idea, without UUOC:
<input.txt sed 's/"pattern"/"new pattern"/g' >output.txt
todo
Now you need to embed this line in your program. You may want to make it interactive, or a command that you could use with 3 parameters.
edit
I tried to avoid the use of output.txt as a temporary file with this:
<input.txt sed 's/"pattern"/"new pattern"/g' >input.txt
but it empties input.txt for a reason I can't understand. So I tried with a subshell, so:
echo $(<input.txt sed 's/pattern/"new pattern"/g')>input.txt
... but the echo command removes line breaks... still looking.
edit2
From https://unix.stackexchange.com/questions/11067/is-there-a-way-to-modify-a-file-in-place , it looks like writing to the very same file at once it not easy at all. However, I could do what I wanted with sed -i for linux only:
sed -i 's/pattern/"new pattern"/g' input.txt
From sed -i + what the same option in SOLARIS , it looks like there's no alternative, and you must use a temporary file:
sed 's/pattern/"new pattern"/g' input.txt > input.tmp && mv input.tmp input.txt
Assuming an ini-style file like this,
[Group]
Icon=xxx.ico
Title=An Image Editor
Description=Manipulates .ico, .png and .jpeg images
I want to replace/delete ".ico" ONLY in the line that starts with (or matches) "Icon="
I was trying this:
oldline="`cat "$file" | grep "Icon="`"
newline="`echo "$oldline" | tr ".ico" ".png"`"
cat "$oldfile" | tr "$oldline" "$newline" > $file
Then i realized that tr works completely different than i thought. Its NOT a tradicional "replace this for that" function. So i guess the correct way is using sed. But:
Ive never used sedbefore. No idea how it works. Is it overkill?
If the most indicated way is really using sed, given it is so powerful, is there any elegant way to accomplish this rather than this "fetch line -> modify line -> replace oldline for newline in file" approach?
Notes:
I cant replace ".ico" globally, i know that would be a LOT easier, i must restrict the replace to the Icon line, otherwise the Description line would be changed too.
Im new to shell scripting in Linux, so im looking not only to the solution itself, but also for the "proper" way to do it. Elegant, easy to read, conventional, etc
Thanks in advance!
Edit:
Thank you guys! Here is the final script, as a reference:
#! /bin/bash
# Fix the following WARNING in ~/.xsession-errors
# gnome-session[2035]: EggSMClient-WARNING: Desktop file '/home/xxx/.config/autostart/skype.desktop' has malformed Icon key 'skype.png'(should not include extension)
file="$HOME/.config/autostart/skype.desktop"
if [ -f "$file" ] ; then
if `cat "$file" | grep "Icon=" | grep -q ".png"` ; then
sed -i.bak '/^Icon=/s/\.png$//' "$file"
cp "$file" "$PWD"
cp "${file}.bak" "$PWD"
else
echo "Nothing to fix! (maybe fixed already?)"
fi
else
echo "Skype not installed (yet...)"
fi
MUCH sleeker than my original! The only thing i regret is that sed backup does not preserve original file timestamp. But i can live with that.
And, for the record, yes, ive created this script to fix an actual "bug" in Skype packaging.
Something like the following in sed should do what you need. First we check if the line starts with Icon= and if it does then we run the s command (i.e. substitute).
sed -i '/^Icon=/s/\.ico$/.png/' file
Edit: The sed script above can also be written like this:
/^Icon=/ { # Only run the following block when this matches
s/\.ico$/.png/ # Substitute '.ico' at the end of the line with '.png'
}
See this page for more details on how to restrict when commands are run.
sed is pretty easy to deal with. Here's one way:
sed 's/^\(Icon=.*\)\.ico$/\1.png/'
By default, sed works on every line in the file one at a time. The 's/.../.../' will do a regular expression match on the first argument and replace it with the second argument. The \1 stands for everything that matched the first group, which is demarcated by the parenthesis. You have to escape the parens with \.
The above works as part of a pipeline, but you can add an '-i' flag, like this
sed -i 's/^\(Icon=.*\)\.ico$/\1.png/' input.txt
to have it replace the file input.txt in place. Don't add that until you have tested your sed script a little.