Take the 2-minute tour ×
Unix & Linux Stack Exchange is a question and answer site for users of Linux, FreeBSD and other Un*x-like operating systems.. It's 100% free, no registration required.

How would one run a specific command for each file that was found by using the find command? For the purpose of the question lets say that I would simply like to delete each file found by find.

I am unix/linux noob so be gentle with me.

share|improve this question

4 Answers 4

up vote 13 down vote accepted

The best way to do this is usually to use the various -exec options to the find command. In particular you should try to use -execdir whenever possible since it runs inside the directory of the file that was found and is generally safer (in the sense of preventing stupid mistakes being disasterous) than other options.

The -exec options are followed by the command you would like to run with {} denoting the spot where the file found by find should be included and are terminated by either \; to run the command once for each file or + to replace {} with a list of arguments of all the matches. Note that the semicolon terminator is escaped so that it is not understood by the shell to be a separator leading to a new command.

Lets say you were finding all text files:

find -iname '*.txt' -execdir rm {} \;

Here is the relevant bit from the find manual (man find):

   -exec command ;
          Execute  command;  true  if 0 status is returned.  All following
          arguments to find are taken to be arguments to the command until
          an  argument  consisting of ‘;’ is encountered.  The string ‘{}’
          is replaced by the current file name being processed  everywhere
          it occurs in the arguments to the command, not just in arguments
          where it is alone, as in some versions of find.  Both  of  these
          constructions might need to be escaped (with a ‘\’) or quoted to
          protect them from expansion by the shell.  See the EXAMPLES sec-
          tion for examples of the use of the -exec option.  The specified
          command is run once for each matched file.  The command is  exe-
          cuted  in  the starting directory.   There are unavoidable secu-
          rity problems surrounding use of the -exec  action;  you  should
          use the -execdir option instead.


   -exec command {} +
          This  variant  of the -exec action runs the specified command on
          the selected files, but the command line is built  by  appending
          each  selected file name at the end; the total number of invoca-
          tions of the command will  be  much  less  than  the  number  of
          matched  files.   The command line is built in much the same way
          that xargs builds its command lines.  Only one instance of  ‘{}’
          is  allowed  within the command.  The command is executed in the
          starting directory.


   -execdir command ;

   -execdir command {} +
          Like -exec, but the specified command is run from the  subdirec-
          tory  containing  the  matched  file,  which is not normally the
          directory in which you started find.  This a  much  more  secure
          method  for invoking commands, as it avoids race conditions dur-
          ing resolution of the paths to the matched files.  As  with  the
          -exec action, the ‘+’ form of -execdir will build a command line
          to process more than one matched file, but any given  invocation
          of command will only list files that exist in the same subdirec-
          tory.  If you use this option, you must ensure that  your  $PATH
          environment  variable  does  not  reference  ‘.’;  otherwise, an
          attacker can run any commands they like by leaving an  appropri-
          ately-named  file in a directory in which you will run -execdir.
          The same applies to having entries in $PATH which are  empty  or
          which are not absolute directory names.
share|improve this answer

You can accomplish this using the xargs command. xargs essentially runs a command once for each instruction of its standard input. So, if you need to delete all .jpg files in a directory for example, a quick way on the command line is:

$ find ./ -name "*.jpg" | xargs rm 

You can also use the backtick (above the Tab button) to do this (note that this is the backquote character, not the single quote character):

$ rm `find ./ -name "*.jpg"`

Note that due to the way xargs and shells process their input, the xargs method only works if none of the file names and directory names involved contain whitespace or any of \"'; the backquote method only works if none of the file names and directory names involved contain whitespace or any of \[?*.

share|improve this answer
3  
Both of these methods are potentially very dangerous, especially the backtick one. There are numerous potential problems with un-escaped characters in file names that could cause these methods to break. –  Caleb Dec 2 '11 at 10:41
1  
I see your point, but these commands can also be used along with other tools besides find, so I think they are worth mentioning here. –  IG83 Dec 2 '11 at 10:59
    
They might be worth mentioning, but when not to use them is important to specify. The OP's question here specifically asked for handling the output of find, for which -exec is generally a better solution. If you want to specify these as alternates, at least explain how to use find -print0 | xargs -0 for safe file name break handling and elaborate on when to be careful about backticks. –  Caleb Dec 2 '11 at 11:09
    
Welcome to the site by the way, I see this is your first answer. Sorry to jump all over it. It's important to teach people up front with the issues are so they don't make mistakes that are hard to catch later, but I do still remember the days when I didn't understand why this was such a big issue too, so please don't take the correction as personal. –  Caleb Dec 2 '11 at 11:11
2  
Thank you for the welcome! Of course there are no hard feelings, you are certainly right in that -exec is the appropriate way to handle this. I am really beginning to see how great this platform is, you are learning new stuff even from the comments:) –  IG83 Dec 2 '11 at 11:52

Find has a built in delete command if that is all you need to do.

find . -name "*.txt" -delete

Any .txt file found will be deleted using the command above.

share|improve this answer

An alternative is to pipe the output and parse it with subsequent commands. The only safe way to do so is to use the -print0 option, which tells find to use a null character as the results delimiter. The receiving commands must have a ability to recognize null delimited input. Example:

find /home/phunehehe -iregex '.*\.png$' -print0 | xargs -0 file

Note that the -0 option tells xargs to treat the input as null delimited.

share|improve this answer
    
You can -exec with more files if you end it with + instead of ;. See caleb's answer. –  Kevin Dec 2 '11 at 12:44
    
@Kevin you are right, I updated the answer. –  phunehehe Dec 2 '11 at 15:21

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.