Find - Revision history

Psmay at 20:04, 9 January 2017

2017-01-09T20:04:16Z

Psmay: /* dos2unix/unix2dos */

2016-02-15T12:43:15Z

dos2unix/unix2dos

Psmay: /* =dos2unix/unix2dos */

2015-11-13T15:02:02Z

=dos2unix/unix2dos

Psmay: /* find and replace */

2015-11-13T15:01:43Z

find and replace

Psmay: /* Using -exec as a for-each mechanism */

2014-11-20T20:25:05Z

Using -exec as a for-each mechanism

New page

{{lowercase|title=find}}{{unix}}

'''find''' is a [[unix]] program that lists files found recursively under a path.

==Null-terminated output==

See [[null-terminated (console)]].

==Unsorted notes==

Until I have time to properly document this, mess with it. Try some of the following:

# Lists files in and below your home directory
find ~/

If the path to be searched is ".", that parameter can usually be omitted.

# Lists files in and below the current directory
find .
# or
find

# Lists only the regular files (no dirs, symlinks, pipes, and so on)
find . -type f

# Lists only the dirs
find . -type d

# Lists regular files and symlinks
find . -type f -o -type l
# or, as a component to something more complex,
find . $ -type f -o -type l $

To run a command on each path found, use -exec. This example runs [[md5sum]] for all regular files (not symlinks, not directories, ...) in and below the current directory, if the read permissions are okay:

find . -type f -exec md5sum {} \; > ../MD5SUMS

The list of files can also be piped to [[xargs]] or [[perl]]; if using either one, use the -print0 condition on find to use null bytes as delimiters, then use the -0 switch on xargs or perl to expect the same.

# Use \0 as a delimiter instead of \n
find . $ -type f -o -type l $ -print0 | perl -n -0 -E 'dosomethingwith($_)'

==Using <code>-exec</code> as a for-each mechanism==

The predicate <code>-exec</code> runs a command for each filename found. When in use, the <code>-print</code> predicate is no longer implied. <code>-exec</code> is used as such:

<syntaxhighlight lang=bash>
find ... -exec command [someargs] {} [otherargs] ';' ...
</syntaxhighlight>

For every filename filename found, the command

<syntaxhighlight lang=bash>
command [someargs] filename [otherargs]
</syntaxhighlight>

would be run. The <code>{}</code> and the <code>';'</code> are not optional, while [someargs] and [otherargs] are optional.

Note that when passing arguments to an inline sh/bash script an extra argument should be used to fill the $0 argument if "$@" is being used:

<syntaxhighlight lang=bash>
find ... -exec sh -c 'echo "$@"' "$0" {} ';'
</syntaxhighlight>

===find and replace===

Using [[sed]]:

<syntaxhighlight lang=bash>
find ... -exec sed -i.orig 's/PATTERN/REPLACEMENT/g' {} ';'
</syntaxhighlight>

Using [[perl]]:

<syntaxhighlight lang=bash>
find ... -exec perl -p -i.orig -e 's/PATTERN/REPLACEMENT/g' {} ';'
</syntaxhighlight>

Replace <code>-i.orig</code> with <code>-i</code> to suppress backups while still changing files in place.

===Call a shell function (bash only)===

In bash (but not plain sh) we can export a bash function with <code>export -f</code> and use it with <code>-exec</code> via a special invocation of bash:

<syntaxhighlight lang=bash>
#!/bin/bash

# Define a function
somefunc() {
...
}

# Export the function to subshells
export -f somefunc

# Call from find
find ... -exec bash -c 'somefunc "$0"' {} ';'
</syntaxhighlight>

==Output relative URIs==

Perl's URI::file knows how to convert a local file to a properly escaped URI.

find '...' -print0 | perl -0 -MURI::file -n -E 'chomp; say "".URI::file->new($_)'

==Combining with Perl on the command line==

Use [[perl]]'s -0 switch to allow -print0 to be treated as lines.

This line prints file modified times (<code>([[perlfunc:stat|stat]](file))[9]</code> gets the mtime):

find -print0 | perl -n0e '$m=(stat("$_"))[9]; printf(q(%12s %s)."\n",$m,$_)'

You may also find my [[except-most-recent]] script handy if you find yourself writing a lot of backup rotation scripts.

==See also==

* [[xargs]], which turns the output of this program into command line arguments.

← Older revision		Revision as of 20:04, 9 January 2017
Line 110:		Line 110:

	find '...' -print0 \| perl -0 -MURI::file -n -E 'chomp; say "".URI::file->new($_)'		find '...' -print0 \| perl -0 -MURI::file -n -E 'chomp; say "".URI::file->new($_)'
		+
		+	==Sorting by mtime==
		+
		+	find won't sort by mtime by itself. This general command produces a sorted result that should be acceptable by anything that would accept the result of `find … -print0`:
		+
		+	# Let $DESTZ be a command that accepts a list of null-terminated filenames
		+	find … -printf '%T@ %p\0' \| sort -zk 1n[r] \| sed -z 's/^[^ ]* //' \| $DESTZ
		+
		+	such as:
		+
		+	find -type f -printf '%T@ %p\0' \| sort -zk 1n \| sed -z 's/^[^ ]* //' \| xargs -0 -i echo 'File: {}'
		+
		+	Breakdown:
		+
		+	# Note that the intermediate processing steps use \0-terminated lists in
		+	# order not to lose information about oddly named files.
		+	find … -printf '%T@ %p\0' \| # Prefixes all files with their numeric mtime and a space
		+	sort -zk 1n[r] \| # Sorts lines numerically by the prefixes (use `1n` for old to new or `1nr` for new to old)
		+	sed -z 's/^[^ ]* //' \| # Strips the prefixes from the sorted result
		+	$DESTZ # Accepts list of null-terminated filenames

	==Combining with Perl on the command line==		==Combining with Perl on the command line==

@@ Line 79: / Line 79: @@
 Replace <code>-i.orig</code> with <code>-i</code> to suppress backups while still changing files in place.
-===dos2unix/unix2dos===
+===[[dos2unix]]/[[unix2dos]]===
 <syntaxhighlight lang=bash>
 find ... -exec dos2unix {} ';'
 </syntaxhighlight>

@@ Line 79: / Line 79: @@
 Replace <code>-i.orig</code> with <code>-i</code> to suppress backups while still changing files in place.
-===dos2unix/unix2dos==
+===dos2unix/unix2dos===
 <syntaxhighlight lang=bash>

← Older revision		Revision as of 15:01, 13 November 2015
Line 78:		Line 78:

	Replace <code>-i.orig</code> with <code>-i</code> to suppress backups while still changing files in place.		Replace <code>-i.orig</code> with <code>-i</code> to suppress backups while still changing files in place.
		+
		+	===dos2unix/unix2dos==
		+
		+	<syntaxhighlight lang=bash>
		+	find ... -exec dos2unix {} ';'
		+	</syntaxhighlight>

	===Call a shell function (bash only)===		===Call a shell function (bash only)===