Executing a command

The find command can be coupled with many of the other commands using the -exec option.

Consider the previous example. We used -perm to find files that do not have proper permissions. Similarly, in the case where we need to change the ownership of all files owned by a certain user (for example, root) to another user (for example, www-data, the default Apache user in the web server), we can find all the files owned by root using the -user option and use -exec to perform the ownership change operation.

You must run the find command as root if you want to change the ownership of files or directories.

The find command uses an open/close curly brace pair {} to represent the filename. In the next example, each time find identifies a file it will replace the {} with the filename and change the ownership of the file. For example, if the find command finds two files with the root owner it will change both so they're owned by slynux:

# find . -type f -user root -exec chown slynux {} \;

Note that the command is terminated with \;. The semicolon must be escaped or it will be grabbed by your command shell as the end of the find command instead of the end of the chown command.

Invoking a command for each file is a lot of overhead. If the command accepts multiple arguments (as chown does) you can terminate the command with a plus (+) instead of a semicolon. The plus causes find to make a list of all the files that match the search parameter and execute the application once with all the files on a single command line.

Another usage example is to concatenate all the C program files in a given directory and write them to a single file, say, all_c_files.txt. Each of these examples will perform this action:

$ find . -type f -name '*.c' -exec cat {} \;>all_c_files.txt
$ find . -type f -name '*.c' -exec cat {} > all_c_files.txt \;
$ fine . -type f -name '*.c' -exec cat {} >all_c_files.txt +

To redirect the data from find to the all_c_files.txt file, we used the > operator instead of >> (append) because the entire output from the find command is a single data stream (stdin); >> is necessary when multiple data streams are to be appended to a single file.

The following command will copy all the .txt files that are older than 10 days to a directory OLD:

$ find . -type f -mtime +10 -name "*.txt" -exec cp {} OLD  \;

The find command can be coupled with many other commands.

We cannot use multiple commands along with the -exec parameter. It accepts only a single command, but we can use a trick. Write multiple commands in a shell script (for example, commands.sh) and use it with -exec as follows:

-exec ./commands.sh {} \;

The -exec parameter can be coupled with printf to produce joutput. Consider this example:

$ find . -type f -name "*.txt" -exec printf "Text file: %s\n" {} \;
Config file: /etc/openvpn/easy-rsa/openssl-1.0.0.cnf
Config file: /etc/my.cnf

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