I would like to run a find and replace on an HTML file through the command line.
My command looks something like this:
sed -e s/STRING_TO_REPLACE/STRING_TO_REPLACE_IT/g index.html > index.html
When I run this and look at the file afterward, it is empty. It deleted the contents of my file.
When I run this after restoring the file again:
sed -e s/STRING_TO_REPLACE/STRING_TO_REPLACE_IT/g index.html
The stdout is the contents of the file, and the find and replace has been executed.
Why is this happening?
When the shell sees > index.html in the command line it opens the file index.html for writing, wiping off all its previous contents.
To fix this you need to pass the -i option to sed to make the changes inline and create a backup of the original file before it does the changes in-place:
sed -i.bak s/STRING_TO_REPLACE/STRING_TO_REPLACE_IT/g index.html
Without the .bak the command will fail on some platforms, such as Mac OSX.
An alternative, useful, pattern is:
sed -e 'script script' index.html > index.html.tmp && mv index.html.tmp index.html
That has much the same effect, without using the -i option, and additionally means that, if the sed script fails for some reason, the input file isn't clobbered. Further, if the edit is successful, there's no backup file left lying around. This sort of idiom can be useful in Makefiles.
Quite a lot of seds have the -i option, but not all of them; the posix sed is one which doesn't. If you're aiming for portability, therefore, it's best avoided.
sed -i 's/STRING_TO_REPLACE/STRING_TO_REPLACE_IT/g' index.html
This does a global in-place substitution on the file index.html. Quoting the string prevents problems with whitespace in the query and replacement.
use sed's -i option, e.g.
sed -i bak -e s/STRING_TO_REPLACE/REPLACE_WITH/g index.html
To change multiple files (and saving a backup of each as *.bak):
perl -p -i -e "s/\|/x/g" *
will take all files in directory and replace | with x
this is called a “Perl pie” (easy as a pie)
You should try using the option -i for in-place editing.
Warning: this is a dangerous method! It abuses the i/o buffers in linux and with specific options of buffering it manages to work on small files. It is an interesting curiosity. But don't use it for a real situation!
Besides the -i option of sed
you can use the tee utility.
From man:
tee - read from standard input and write to standard output and files
So, the solution would be:
sed s/STRING_TO_REPLACE/STRING_TO_REPLACE_IT/g index.html | tee | tee index.html
-- here the tee is repeated to make sure that the pipeline is buffered. Then all commands in the pipeline are blocked until they get some input to work on. Each command in the pipeline starts when the upstream commands have written 1 buffer of bytes (the size is defined somewhere) to the input of the command. So the last command tee index.html, which opens the file for writing and therefore empties it, runs after the upstream pipeline has finished and the output is in the buffer within the pipeline.
Most likely the following won't work:
sed s/STRING_TO_REPLACE/STRING_TO_REPLACE_IT/g index.html | tee index.html
-- it will run both commands of the pipeline at the same time without any blocking. (Without blocking the pipeline should pass the bytes line by line instead of buffer by buffer. Same as when you run cat | sed s/bar/GGG/. Without blocking it's more interactive and usually pipelines of just 2 commands run without buffering and blocking. Longer pipelines are buffered.) The tee index.html will open the file for writing and it will be emptied. However, if you turn the buffering always on, the second version will work too.
sed -i.bak "s#https.*\.com#$pub_url#g" MyHTMLFile.html
If you have a link to be added, try this. Search for the URL as above (starting with https and ending with.com here) and replace it with a URL string. I have used a variable $pub_url here. s here means search and g means global replacement.
It works !
The problem with the command
sed 'code' file > file
is that file is truncated by the shell before sed actually gets to process it. As a result, you get an empty file.
The sed way to do this is to use -i to edit in place, as other answers suggested. However, this is not always what you want. -i will create a temporary file that will then be used to replace the original file. This is problematic if your original file was a link (the link will be replaced by a regular file). If you need to preserve links, you can use a temporary variable to store the output of sed before writing it back to the file, like this:
tmp=$(sed 'code' file); echo -n "$tmp" > file
Better yet, use printf instead of echo since echo is likely to process \\ as \ in some shells (e.g. dash):
tmp=$(sed 'code' file); printf "%s" "$tmp" > file
And the ed answer:
printf "%s\n" '1,$s/STRING_TO_REPLACE/STRING_TO_REPLACE_IT/g' w q | ed index.html
To reiterate what codaddict answered, the shell handles the redirection first, wiping out the "input.html" file, and then the shell invokes the "sed" command passing it a now empty file.
I was searching for the option where I can define the line range and found the answer. For example I want to change host1 to host2 from line 36-57.
sed '36,57 s/host1/host2/g' myfile.txt > myfile1.txt
You can use gi option as well to ignore the character case.
sed '30,40 s/version/story/gi' myfile.txt > myfile1.txt
With all due respect to the above correct answers, it's always a good idea to "dry run" scripts like that, so that you don't corrupt your file and have to start again from scratch.
Just get your script to spill the output to the command line instead of writing it to the file, for example, like that:
sed -e s/STRING_TO_REPLACE/STRING_TO_REPLACE_IT/g index.html
OR
less index.html | sed -e s/STRING_TO_REPLACE/STRING_TO_REPLACE_IT/g
This way you can see and check the output of the command without getting your file truncated.
in my script i edit a file by using "sed":
sed -i -e /NumberOfEntries=*/d "$playlist_name" > /dev/null # deletes "NumberOfEntries"-line
sed -i -e '/^$/d' "$playlist_name" > /dev/null # deletes all empty lines
This works just fine but while execution (and shortly after) there are one or two temporary files named something like "sedJjHEt2" (the string after sed changes everytime i run the script). The file is marked with a lock and red X-Symbol.
Is there a way to turn this off or am I missing something that I need to adjust? Or is this because of the "-i" Option?
Thanks in advance!
Because of the "-i" Option.
once you use "-i", sed will create a temporary, and then replace the original file with the temporary file.
I have a problem: I have a file that, if I knew how, I would like to edit from the command. I would like to locate the file by content on that line.
I am in CyberPatriot, and my team is second in my state. I know someone who is on the number one team and I know one of the people on the first team. It kills me so I want to make a list of commands that I can go off of to make it faster and more efficient.
Imagine I had this file:
example
oof
goo
random
yes
and I wanted to change it to this:
example
oof
goo
random 'added text'
yes
How do I do so?
I know I can use the echo command to add text to the end of a file, but I don't know how to add text to the end of a specific line.
Thanks, Owen
You can use sed for this purpose.
sed 's/random/& Hello World/' file
to append text to the matched string.
You can use ^random$ to make sure the entire line is matched, before appending.
If you need to modify the file directly, you can use the -i flag, which facilitates in-place editing. Further, using -i.bak creates a backup of the original file first before modifying it, as in
sed -i.bak 's/random/& Hello World/' file
The original copy of the file can be found in file.bak
More about sed : https://www.gnu.org/software/sed/manual/sed.html
Use something like below
sed '4!d' file | xargs -I{} sed -i "4s/{}/{} \'added text\'/" file
Basically in the above command, we are getting the 4th line of the file using sed sed '4!d' file and then using this line to replace it with the same text and some new text(added text)
My Dockerfile's entry point CMD executes a shell script to modify a local file based on an environment variable before executing my application (Flask). The shell script is like so:
cat static/login.html | sed "s/some_match/some_substitute/g" > static/login.html
However, I am finding that the resulting file is zero bytes. Any ideas what might be going on?
Thanks.
I can reproduce your problem, but not explain it. Maybe other answers follow.
But here is a solution which fixes the problem:
Use a different file name for the output than for the input.
cat input.txt | sed "s/a/b/g" > input2.txt
Alternatively, use the -i.bak option.
sed -i.bak "s/b/a/g" input.txt
I can only speculate about what exactly is going on:
Maybe the output of your pipe is opened for writing (non-appending) before the input is read.
I have a configure file which has a line ServerIP= in it. Now I want to use find this line and add a new IP address to it, i.e. replace it with ServerIP=192.168.0.101, what is the command like?
You can employ a find-and-replace command to do this:
sed -e 's/\(^ServerIP=\)/\1192.168.0.101/g' your_file
Are we doing this all over the file or only in one spot? The command above should replace it everywhere. You will have to send the output somewhere. I never edit in place with sed because I make too many mistakes.
One tricky thing is this part, \1192.168.0.101, which actually can be broken down like this:
\1 --> the thing we captured
192.168.0.101 --> the thing we are placing IMMEDIATELY after the thing we captured
Also, you may have other lines that look a little different. But, in the future, look up "sed capture and replace".
This one would work whether there's an existing value in ServerIP or not:
sed -i 's#\([[:blank:]]*ServerIP=\)[[:digit:].]*#\1192.168.0.101#' file
I also suggest that you try to learn using CLI editors like VIM or Nano instead.
try:
sed -i 's/^ *ServerIP=/&192.168.0.101/' file
I would do:
sed -i 's/^ServerIP=$/ServerIP=192.168.0.101/' file.config