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Linux in a Nutshell

This directory of Linux commands is from Linux in a Nutshell, 5th Edition.

Click on any of the 687 commands below to get a description and list of available options. All links in the command summaries point to the online version of the book on Safari Bookshelf.

Buy it now, or read it online on Safari Bookshelf.



find

find [pathnames] [conditions]

An extremely useful command for finding particular groups of files (numerous examples follow this description). find descends the directory tree beginning at each pathname and locates files that meet the specified conditions. The default pathname is the current directory. The most useful conditions include -name and -type (for general use), -exec and -size (for advanced use), and -mtime and -user (for administrators).

Conditions may be grouped by enclosing them in \( \) (escaped parentheses), negated with !, given as alternatives by separating them with -o, or repeated (adding restrictions to the match; usually only for -name, -type, or -perm). Note that "modification" refers to editing of a file's contents, whereas "change" means a modification, or permission or ownership changes. In other words, -ctime is more inclusive than -atime or -mtime.

Conditions and actions

-amin +n| -n| n

Find files last accessed more than n (+n), less than n (-n), or exactly n minutes ago.

-anewer file

Find files that were accessed after file was last modified. Affected by -follow when after -follow on the command line.

-atime +n| -n| n

Find files that were last accessed more than n (+n), less than n (-n), or exactly n days ago. Note that find changes the access time of directories supplied as pathnames.

-cmin +n| -n| n

Find files last changed more than n (+n), less than n (-n), or exactly n minutes ago.

-cnewer file

Find files that were changed after they were last modified. Affected by -follow when after -follow on the command line.

-ctime +n| -n| n

Find files that were changed more than n (+n), less than n (-n), or exactly n days ago. A change is anything that changes the directory entry for the file, such as a chmod.

-daystart

Calculate times from the start of the day today, not 24 hours ago.

-depth

Descend the directory tree, skipping directories and working on actual files first, and then the parent directories. Useful when files reside in unwritable directories (e.g., when using find with cpio).

-empty

Continue if file is empty. Applies to regular files and directories.

-exec command{ } \ ;

Run the Linux command, from the starting directory on each file matched by find (provided command executes successfully on that file—i.e., returns a 0 exit status). When command runs, the argument { } substitutes the current file. Follow the entire sequence with an escaped semicolon (\;). In some shells, the braces may need to be escaped as well.

-false

Return false value for each file encountered.

-follow

Follow symbolic links and track the directories visited (don't use with -type l).

-fstype type

Match files only on type filesystems. Acceptable types include minix, ext, ext2, xia, msdos, umsdos, vfat, proc, nfs, iso9660, hpfs, sysv, smb, and ncpfs.

-gid num

Find files with numeric group ID of num.

-group gname

Find files belonging to group gname. gname can be a group name or a group ID number.

-ilname pattern

A case-insensitive version of -lname.

-iname pattern

A case-insensitive version of -name.

-inum n

Find files whose inode number is n.

-ipath pattern

A case-insensitive version of -path.

-iregex pattern

A case-insensitive version of -regex.

-links n

Find files having n links.

-lname pattern

Search for files that are symbolic links, pointing to files named pattern. pattern can include shell metacharacters and does not treat / or . specially. The match is case-insensitive.

-maxdepth num

Do not descend more than num levels of directories.

-mindepth num

Begin applying tests and actions only at levels deeper than num levels.

-mmin +n| -n| n

Find files last modified more than n (+n), less than n (-n), or exactly n minutes ago.

-mount, -xdev

Search only for files that reside on the same filesystem as pathname.

-mtime +n| -n| n

Find files that were last modified more than n (+n), less than n (-n), or exactly n days ago. A modification is a change to a file's data.

-name pattern

Find files whose names match pattern. Filename metacharacters may be used but should be escaped or quoted.

-newer file

Find files that were modified more recently than file; similar to -mtime. Affected by -follow only if it occurs after -follow on the command line.

-nogroup

The file's group ID does not correspond to any group.

-noleaf

Normally, find assumes that each directory has at least two hard links that should be ignored (a hard link for its name and one for "."--i.e., two fewer "real" directories than its hard link count indicates). -noleaf turns off this assumption, a useful practice when find runs on non-Unix-style filesystems. This forces find to examine all entries, assuming that some might prove to be directories into which it must descend (a time-waster on Unix).

-nouser

The file's user ID does not correspond to any user.

-ok command { }\;

Same as -exec, but prompts user to respond with y before command is executed.

-path pattern

Find files whose names match pattern. Expect full pathnames relative to the starting pathname (i.e., do not treat / or . specially).

-perm nnn

Find files whose permission flags (e.g., rwx) match octal number nnn exactly (e.g., 664 matches -rw-rw-r--). Use a minus sign before nnn to make a "wildcard" match of any unspecified octal digit (e.g., -perm -600 matches -rw-******, where * can be any mode).

-print

Print the matching files and directories, using their full pathnames. Return true. This is the default behavior.

-regex pattern

Like -path, but uses grep-style regular expressions instead of the shell-like globbing used in -name and -path.

-size n[c]

Find files containing n blocks, or if c is specified, n characters long.

-type c

Find files whose type is c. c can be b (block special file), c (character special file), d (directory), p (fifo or named pipe), l (symbolic link), s (socket), or f (plain file).

-user user

Find files belonging to user (name or ID).

Examples

List all files (and subdirectories) in your home directory:

find $HOME -print

List all files named chapter1 in the /work directory:

find /work -name chapter1

List all files beginning with memo owned by ann:

find /work -name 'memo*' -user ann -print

Search the filesystem (begin at root) for manpage directories:

find / -type d -name 'man*' -print

Search the current directory, look for filenames that don't begin with a capital letter, and send them to the printer:

find . \! -name '[A-Z] *' -exec lpr { }\;

Find and compress files whose names don't end with .gz:

gzip `find . \! -name '*.gz' -print`

Remove all empty files on the system (prompting first):

find / -size 0 -ok rm { } \;

Search the system for files that were modified within the last two days (good candidates for backing up):

find / -mtime -2 -print

Recursively grep for a pattern down a directory tree:

find /book -print | xargs grep '[Nn] utshell'

If the files kt1 and kt2 exist in the current directory, their names can be printed with the command:

$ find . -name 'kt[0-9] ' ./kt1 ./kt2

Since the command prints these names with an initial ./ path, you need to specify the ./ when using the -path option:

$ find . -path './kt[0-9] ' ./kt1 ./kt2

The -regex option uses a complete pathname, like -path, but treats the following argument as a regular expression rather than a glob pattern (although in this case the result is the same):

$ find . -regex './kt[0-9] ' ./kt1 ./kt2