I am using the following to search a directory recursively for specific string and replace it with another:
grep -rl oldstr path | xargs sed -i 's/oldstr/newstr/g'
This works okay. The only problem is that if the string doesn't exist then sed fails because it doesn't get any arguments. This is a problem for me since i'm running this automatically with ANT and the build fails since sed fails.
Is there a way to make it fail-proof in case the string is not found?
I'm interested in a one line simple solution I can use (not necessarily with grep or sed but with common unix commands like these).
I think that without using -exec you can simply provide /dev/null as at least one argument in case nothing is found:
grep -rl oldstr path | xargs sed -i 's/oldstr/newstr/g' /dev/null
Standard xargs has no good way to do it; you're better off using find -exec as someone else suggested, or wrap the sed in a script which does nothing if there are no arguments. GNU xargs has the --no-run-if-empty option, and BSD / OS X xargs has the -L option which looks like it should do something similar.
I have taken Vlad's idea and changed it a little bit. Instead of
grep -rl oldstr path | xargs sed -i 's/oldstr/newstr/g' /dev/null
Which yields
sed: couldn't edit /dev/null: not a regular file
I'm doing in 3 different connections to the remote server
touch deleteme
grep -rl oldstr path | xargs sed -i 's/oldstr/newstr/g' ./deleteme
rm deleteme
Although this is less elegant and requires 2 more connections to the server (maybe there's a way to do it all in one line) it does the job efficiently as well
Your solution is ok. only try it in this way:
files=$(grep -rl oldstr path) && echo $files | xargs sed....
so execute the xargs only when grep return 0, e.g. when found the string in some files.
My use case was I wanted to replace
foo:/Drive_Letter with foo:/bar/baz/xyz
In my case I was able to do it with the following code.
I was in the same directory location where there were bulk of files.
find . -name "*.library" -print0 | xargs -0 sed -i '' -e 's/foo:\/Drive_Letter:/foo:\/bar\/baz\/xyz/g'
hope that helped.
Not sure if this will be helpful but you can use this with a remote server like the example below
ssh example.server.com "find /DIR_NAME -type f -name "FILES_LOOKING_FOR" -exec sed -i 's/LOOKINGFOR/withThisString/g' {} ;"
replace the example.server.com with your server replace DIR_NAME with your directory/file locations replace FILES_LOOKING_FOR with files you are looking for replace LOOKINGFOR with what you are looking for replace withThisString with what your want to be replaced in the file
If you are to replace a fixed string or some pattern, I would also like to add the bash builtin pattern string replacement variable substitution construct. Instead of describing it myself, I am quoting the section from the bash manual:
${parameter/pattern/string}The pattern is expanded to produce a pattern just as in pathname expansion. parameter is expanded and the longest match of pattern against its value is replaced with string. If pattern begins with
/, all matches of pattern are replaced with string. Normally only the first match is replaced. If pattern begins with#, it must match at the beginning of the expanded value of parameter. If pattern begins with%, it must match at the end of the expanded value of parameter. If string is null, matches of pattern are deleted and the/following pattern may be omitted. If parameter is@or*, the substitution operation is applied to each positional parameter in turn, and the expansion is the resultant list. If parameter is an array variable subscripted with@or*, the substitution operation is applied to each member of the array in turn, and the expansion is the resultant list.
Source: Stackoverflow.com