Awk - Revision history

Admin: /* Renaming Files, If Names Not Duplicates */

2017-03-25T03:11:31Z

Renaming Files, If Names Not Duplicates

← Older revision		Revision as of 03:11, 25 March 2017
Line 253:		Line 253:

	<pre>		<pre>
	~~$ touch filename1~~

	$ echo "filename1 filename2" \| awk '{ if ( $1 == $2 ) print ""; else print $0; }' \| xargs -r -n2 -t mv		$ echo "filename1 filename2" \| awk '{ if ( $1 == $2 ) print ""; else print $0; }' \| xargs -r -n2 -t mv
	mv filename1 filename2		mv filename1 filename2

Admin: /* Renaming Files, If Names Not Duplicates */

2017-03-25T03:11:01Z

Renaming Files, If Names Not Duplicates

← Older revision		Revision as of 03:11, 25 March 2017
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	==Renaming Files, If Names Not Duplicates==		==Renaming Files, If Names Not Duplicates==

	I wanted to transform some filenames in a directory using a sed script (see [[Sed#Renaming_files]]). However, I had ~~to change~~ the script ~~later and re-run it~~. ~~This caused a problem~~, ~~because Sed would~~ not change the ~~name~~, so the ~~arguments being fed to~~ <code>~~xargs~~ mv</code> ~~were duplicates. Thus~~, I would ~~see a bunch of this junk~~:		I wanted to transform some filenames in a directory using a sed script (see [[Sed#Renaming_files]]). However, the sed script had already been run, and some of the files had transformed filenames, while there were also new files that the sed script would need to rename.

			Unfortunately, if sed did not change the filename, and it was passed to the <code>mv</code> command, it would result in error messages:

	<pre>		<pre>

Admin: /* Renaming Files, If Names Not Duplicates */

2017-03-25T03:09:07Z

Renaming Files, If Names Not Duplicates

← Older revision		Revision as of 03:09, 25 March 2017
Line 250:		Line 250:
	Here's its use in an actual example:		Here's its use in an actual example:

	<~~awk~~>		<pre>
	$ touch filename1		$ touch filename1

Line 258:		Line 258:
	$ echo "filename2 filename2" \| awk '{ if ( $1 == $2 ) print ""; else print $0; }' \| xargs -r -n2 -t mv		$ echo "filename2 filename2" \| awk '{ if ( $1 == $2 ) print ""; else print $0; }' \| xargs -r -n2 -t mv

	</~~awk~~>		</pre>

	(Note that the <code>-r</code> flag for <code>xargs</code> tells it not to run the command if there are no input arguments, so that way it won't run the "mv" command with no arguments).		(Note that the <code>-r</code> flag for <code>xargs</code> tells it not to run the command if there are no input arguments, so that way it won't run the "mv" command with no arguments).

Admin: /* Renaming Files, If Names Not Duplicates */

2017-03-25T03:08:40Z

Renaming Files, If Names Not Duplicates

@@ Line 244: / Line 244: @@
 I don't want to see this.  So, I needed to add a check to make sure the two filenames were not duplicates.  I used Awk to check if the filenames were duplicates.  The Awk script I used was:
-<source lang="bash">
+<pre>
 $ awk '{ if ( $1 == $2 ) print ""; else print $0; }' | xargs -n2 -t mv
-</source>
+</pre>
 Here's its use in an actual example:
-<source lang="bash">
+<awk>
 $ touch filename1
@@ Line 258: / Line 258: @@
 $ echo "filename2 filename2" | awk '{ if ( $1 == $2 ) print ""; else print $0; }' | xargs -r -n2 -t mv
-</source>
+</awk>
 (Note that the <code>-r</code> flag for <code>xargs</code> tells it not to run the command if there are no input arguments, so that way it won't run the "mv" command with no arguments).
@@ Line 282: / Line 282: @@
 The final script looks like this:
-<source lang="bash">
+<pre>
 #!/bin/sh
@@ Line 296: / Line 296: @@
   | awk '{ if( $1 == $2 ) print ""; else print $0 }' \
   | xargs -r -n2 -t mv
-</source>
+</pre>
 = Useful Resources =

Admin at 04:58, 8 July 2011

2011-07-08T04:58:28Z

@@ Line 110: / Line 110: @@
 SUBSEP
 * The subscript separator string for multi-dimensional arrays; the default value is implementation-defined.
 = Examples =

Admin at 15:35, 28 May 2011

2011-05-28T15:35:48Z

← Older revision		Revision as of 15:35, 28 May 2011
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	The one-liners can help if you aren't quite sure how to translate the stuff in the awk man page into an awk program. It is also probable that you'll find a program that you can tweak a little bit to do what you want.		The one-liners can help if you aren't quite sure how to translate the stuff in the awk man page into an awk program. It is also probable that you'll find a program that you can tweak a little bit to do what you want.

	~~[[Category:Computers]]~~
	~~[[Category:Programs]]~~

	~~[[Category:Languages]]~~
	~~[[Category:~~Unix]]
			{{Programs}}
			{{Unix Programs}}
			{{Languages}}

Admin: /* Renaming Files, If Names Not Duplicates */

2011-05-28T05:42:51Z

Renaming Files, If Names Not Duplicates

← Older revision		Revision as of 05:42, 28 May 2011
Line 213:		Line 213:
	$ touch filename1		$ touch filename1

	$ echo "filename1 filename2" \| awk '{ if ( $1 == $2 ) print ""; else print $0; }' \| xargs -n2 -t mv		$ echo "filename1 filename2" \| awk '{ if ( $1 == $2 ) print ""; else print $0; }' \| xargs -r -n2 -t mv
	mv filename1 filename2		mv filename1 filename2

	$ echo "filename2 filename2" \| awk '{ if ( $1 == $2 ) print ""; else print $0; }' \| xargs -n2 -t mv		$ echo "filename2 filename2" \| awk '{ if ( $1 == $2 ) print ""; else print $0; }' \| xargs -r -n2 -t mv

	</source>		</source>

			(Note that the <code>-r</code> flag for <code>xargs</code> tells it not to run the command if there are no input arguments, so that way it won't run the "mv" command with no arguments).

	So the first command, which has two unique arguments, executes the move command. The second command, which has duplicate arguments, does not execute the move command.		So the first command, which has two unique arguments, executes the move command. The second command, which has duplicate arguments, does not execute the move command.
Line 253:		Line 255:
	\| xargs -n2 \		\| xargs -n2 \
	\| awk '{ if( $1 == $2 ) print ""; else print $0 }' \		\| awk '{ if( $1 == $2 ) print ""; else print $0 }' \
	\| xargs -~~I {}~~ -n2 -t mv		\| xargs -r -n2 -t mv
	</source>		</source>

Admin: /* Renaming Files, If Names Not Duplicates */

2011-05-28T05:39:37Z

Renaming Files, If Names Not Duplicates

← Older revision		Revision as of 05:39, 28 May 2011
Line 222:		Line 222:
	So the first command, which has two unique arguments, executes the move command. The second command, which has duplicate arguments, does not execute the move command.		So the first command, which has two unique arguments, executes the move command. The second command, which has duplicate arguments, does not execute the move command.

	~~The final script ended~~ up ~~looking~~ like this:		In the case that the arguments being fed to awk are coming from sed, they are going to be split up into one line each. For this reason, they should first be piped through <code>xargs -n2</code>, so that output from sed that looks like this:

			<pre>
			aaa
			bbb
			ccc
			ddd
			</pre>

			can be fed to awk like this:

			<pre>
			aaa bbb
			ccc ddd
			</pre>

	The final script looks like this:		The final script looks like this:
Line 237:		Line 251:
	-e 's/k$[0-9]\{1\}$$/k00\1/' \		-e 's/k$[0-9]\{1\}$$/k00\1/' \
	-e 's/k$[0-9]\{2\}$$/k0\1/' \		-e 's/k$[0-9]\{2\}$$/k0\1/' \
			\| xargs -n2 \
	\| awk '{ if( $1 == $2 ) print ""; else print $0 }' \		\| awk '{ if( $1 == $2 ) print ""; else print $0 }' \
	\| xargs -I {} -n2 -t mv		\| xargs -I {} -n2 -t mv

Admin: /* Parsing */

2011-05-28T05:31:28Z

Parsing

← Older revision		Revision as of 05:31, 28 May 2011
Line 17:		Line 17:
	You can parse a list using awk by using the <code>-F</code> flag, followed by the delimiter (by default, it is space). Each token can then be referred to using <code>$1, $2, $3,</code> etc.		You can parse a list using awk by using the <code>-F</code> flag, followed by the delimiter (by default, it is space). Each token can then be referred to using <code>$1, $2, $3,</code> etc.

	<~~syntaxhighlight~~ lang="bash">		<source lang="bash">
	$ echo "token1.token2.token3"		$ echo "token1.token2.token3"
	token1.token2.token3		token1.token2.token3
Line 26:		Line 26:
	$ echo "token1.token2.token3" \| awk -F. '{print $2}'		$ echo "token1.token2.token3" \| awk -F. '{print $2}'
	token2		token2
	</~~syntaxhighlight~~>		</source>

	This can be done with any character, not just punctuation:		This can be done with any character, not just punctuation:

	<~~syntaxhighlight~~ lang="bash">		<source lang="bash">
	$ echo "token1atoken2atoken3"		$ echo "token1atoken2atoken3"
	token1atoken2atoken3		token1atoken2atoken3
Line 39:		Line 39:
	$ echo "token1atoken2atoken3" \| awk -Fa '{print $2}'		$ echo "token1atoken2atoken3" \| awk -Fa '{print $2}'
	token2		token2
	</~~syntaxhighlight~~>		</source>

	and to parse via spaces:		and to parse via spaces:

	<~~syntaxhighlight~~ lang="bash">		<source lang="bash">
	$ echo "token1 token2 token3" \| awk -F" " '{print $1}'		$ echo "token1 token2 token3" \| awk -F" " '{print $1}'
	token1		token1
Line 49:		Line 49:
	$ echo "token1 token2 token3" \| awk -F" " '{print $2}'		$ echo "token1 token2 token3" \| awk -F" " '{print $2}'
	token2		token2
	</~~syntaxhighlight~~>		</source>

			'''NOTE''': spaces are the default tokenizer:

			<source lang="bash">
			$ echo "token1 token2 token3" \| awk '{print $1}'
			token1
			</source>

	== Built-In Variables ==		== Built-In Variables ==

Admin: /* Renaming Files, If Names Not Duplicates */

2011-05-28T05:29:38Z

Renaming Files, If Names Not Duplicates

← Older revision		Revision as of 05:29, 28 May 2011
Line 215:		Line 215:
	So the first command, which has two unique arguments, executes the move command. The second command, which has duplicate arguments, does not execute the move command.		So the first command, which has two unique arguments, executes the move command. The second command, which has duplicate arguments, does not execute the move command.

			The final script ended up looking like this:

			The final script looks like this:

			<source lang="bash">
			#!/bin/sh

			ls -1c i* \| /bin/sed \
			-e 'p' \
			-e 's/i$[0-9]\{1\}$_/i00\1_/' \
			-e 's/i$[0-9]\{2\}$_/i0\1_/' \
			-e 's/j$[0-9]\{1\}$_/j00\1_/' \
			-e 's/j$[0-9]\{2\}$_/j0\1_/' \
			-e 's/k$[0-9]\{1\}$$/k00\1/' \
			-e 's/k$[0-9]\{2\}$$/k0\1/' \
			\| awk '{ if( $1 == $2 ) print ""; else print $0 }' \
			\| xargs -I {} -n2 -t mv
	</source>		</source>