find

From Wikipedia, the free encyclopedia

For other uses, see Find (disambiguation).

The find program is a directory search utility on Unix-like platforms. It searches through one or more directory trees of a filesystem, locating files based on some user-specified criteria. By default, find returns all files below the current working directory. Further, find allows the user to specify an action to be taken on each matched file. Thus, it is an extremely powerful program for applying actions to many files. It also supports regex matching.

The locate programs use a database of indexed files obtained through find (updated at regular intervals, typically by cron job) to provide a faster method of searching the entire filesystem for files by name. This sacrifices overall efficiency (because filesystems are regularly interrogated even when no users needs information)and absolute accuracy (since the database is not updated in real time) for significant speed improvements (particularly on very large filesystems). On fast systems with small drives locate is not necessary or desirable.

[edit] Find syntax

find [-H] [-L] [-P] [path...] [expression]

At least one path must precede the expression. Find is capable of interpreting wildcards internally and commands must be constructed carefully in order to control shell globbing.

Expression elements are whitespace-separated and evaluated from left to right. They can contain logical elements such as AND (-a) and OR (-o) as well as more complex predicates.

The GNU find has a large number of additional features not specified by POSIX.

[edit] POSIX protection from infinite output

Real-world filesystems often contain looped structures created through the use of hard or soft links. The POSIX standard requires that

The find utility shall detect infinite loops; that is, entering a previously visited
directory that is an ancestor of the last file encountered. When it detects an infinite
loop, find shall write a diagnostic message to standard error and shall either recover
its position in the hierarchy or terminate.

[edit] Examples

[edit] From current directory

find . -name 'my*'

This searches in the current directory (represented by a period) and below it, for files and directories with names starting with my. The quotes avoid the shell expansion - without them the shell would replace my* with the list of files whose names begin with my in the current directory. In newer versions of the program, the directory may be omitted, and it will imply the current directory.

[edit] Files only

find . -name "my*" -type f

This limits the results of the above search to only regular files, therefore excluding directories, special files, pipes, symbolic links, etc. my* is enclosed in quotes as otherwise the shell would replace it with the list of files in the current directory starting with my...

[edit] Commands

The previous examples created listings of results because, by default, find executes the '-print' action. (Note that early versions of the find command had no default action at all; therefore the resulting list of files would be discarded, to the bewilderment of users.)

find . -name "my*" -type f -ls

This prints an extended file information.

[edit] Search all directories

find / -type f -name "myfile" -print

This searches every file on the computer for a file with the name myfile. It is generally not a good idea to look for data files this way. This can take a considerable amount of time, so it is best to specify the directory more precisely. Some operating systems may mount dynamic filesystems that are not congenial to find.

[edit] Search all but one directory subtree

find / -path excluded_folder -prune -o -type f -name myfile -print

This searches every folder on the computer except the subtree excluded_folder for a file with the name myfile. It will not detect directories, devices, links, doors, or other "special" filetypes.

[edit] Specify a directory

find /home/weedly -name "myfile" -type f -print

This searches for files named myfile in the /home/weedly directory, the home directory for userid weedly. You should always specify the directory to the deepest level you can remember.

[edit] Search several directories

find local /tmp -name mydir -type d -print

This searches for directories named mydir in the local subdirectory of the current working directory and the /tmp directory.

[edit] Ignore errors

If you're doing this as a user other than root, you might want to ignore permission denied (and any other) errors. Since errors are printed to stderr, they can be suppressed by redirecting the output to /dev/null. The following example shows how to do this in the bash shell:

find / -name "myfile" -type f -print 2>/dev/null

If you are a csh or tcsh user, you cannot redirect stderr without redirecting stdout as well. You can use sh to run the find command to get around this:

sh -c find / -name "myfile" -type f -print 2>/dev/null

An alternate method when using csh or tcsh is to pipe the output from stdout and stderr into a grep command. This example shows how to suppress lines that contain permission denied errors.

find . -name "myfile" |& grep -v "Permission denied"

[edit] Find any one of differently named files

find . \( -name "*jsp" -o -name "*java" \) -type f -ls

The -ls option prints extended information, and the example finds any file whose name ends with either 'jsp' or 'java'. Note that the parentheses are required. Also note that the operator "or" can be abbreviated as "o". The "and" operator is assumed where no operator is given. In many shells the parentheses must be escaped with a backslash, "\(" and "\)", to prevent them from being interpreted as special shell characters. The -ls option and the -or operator are not available on all versions of find.

[edit] Execute an action

find /var/ftp/mp3 -name "*.mp3" -type f -exec chmod 644 {} \;

This command changes the permissions of all files with a name ending in .mp3 in the directory /var/ftp/mp3. The action is carried out by specifying the option -exec chmod 644 {} \; in the command. For every file whose name ends in .mp3, the command chmod 644 {} is executed replacing {} with the name of the file. The semicolon (backslashed to avoid the shell interpreting it as a command separator) indicates the end of the command. Permission 644, usually shown as rw-r--r--, gives the file owner full permission to read and write the file, while other users have read-only access. In some shells, the {} must be quoted.

Note that the command itself should *not* be quoted; otherwise you get error messages like

find: echo "mv ./3bfn rel071204": No such file or directory

which means that find is trying to run a file called 'echo "mv ./3bfn rel071204"' and failing.

If you will be executing over many results, it is more efficient to pipe the results to the xargs command instead.

If running under Windows, don't include the backslash before the semicolon:

find . -exec grep blah {} ;

[edit] Search for a string

This command will search for a string in all files from the /tmp directory and below:

find /tmp -exec grep "search string" '{}' /dev/null \; -print

The /dev/null argument is used to show the name of the file before the text that is found. Without it, only the text found is printed. An equivalent mechanism is to use the "-H" or "--with-filename" option to grep:

find /tmp -exec grep -H "search string" '{}' \; -print

GNU grep can be used on its own to perform this task:

grep -r "search string" /tmp

Example of search for "LOG" in jsmith's home directory

find ~jsmith -exec grep "LOG" '{}' /dev/null \; -print
/home/jsmith/scripts/errpt.sh:cp $LOG $FIXEDLOGNAME
/home/jsmith/scripts/errpt.sh:cat $LOG
/home/jsmith/scripts/title:USER=$LOGNAME

Example of search for the string "ERROR" in all xml files in the current directory and all sub-directories

find . -name "*.xml" -exec grep "ERROR" '{}' \; -print

The double quotes (" ") surrounding the search string and single quotes (' ') surrounding the braces are optional in this example, but needed to allow spaces and other special characters in the string.

[edit] Search for all files owned by a user

find . -user <userid>

[edit] See also

locate, a Unix search tool based on a prebuilt database therefore faster and less accurate than find
List of Unix programs
List of DOS commands
find (command), a DOS and Windows command that is very different from UNIX find

[edit] External links

GNU Findutils - Comes with the xargs and locate commands.
Official webpage for GNU find
Softpanorama find tutorial
find(1): search for files in a directory hierarchy – Linux man page
Exercises "Find"
"Find helper" - unix "find" wizard
Guide to Linux Find Command Mastery