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Top Forums UNIX for Dummies Questions & Answers Faster than nested while read loops? Post 302545657 by chstr_14 on Tuesday 9th of August 2011 05:06:46 AM
Old 08-09-2011
Faster than nested while read loops?

Hi experts,
I just want to know if there is a better solution to my nested while read loops below:

Code:
 
while read line; do
    while read line2; do
        while read line3; do
            echo "$line $line2 $line3"
        done < file3.txt
    done < file2.txt
done < file1.txt > output.txt

file1.txt:
1a
1b

file2.txt:
2a
2b

file3.txt:
3a
3b

output.txt:
1a 2a 3a
1a 2a 3b
1a 2b 3a
1a 2b 3b
1b 2a 3a
1b 2a 3b
1b 2b 3a
1b 2b 3b

I am thinking that a perl or an awk script could do this, which are much faster than while loops.

Thanks!
 

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XCLIP-COPYFILE(1)					      General Commands Manual						 XCLIP-COPYFILE(1)

NAME
xclip-copyfile, xclip-cutfile, xclip-pastefile - copy and move files via the X clipboard SYNOPSIS
xclip-copyfile [-p] FILES... xclip-cutfile [-p] FILES... xclip-pastefile DESCRIPTION
xclip-copyfile copies files into the X clipboard, recursing into directories. xclip-cutfile copies the files, but also deletes them afterwards. -p preserve path formation xclip-pastefile pastes the files out of the clipboard EXAMPLES
Copying a file to a remote host [maggie.lkpg.cendio.se ~]$ echo "A file created on ${HOSTNAME}" > file1 [maggie.lkpg.cendio.se ~]$ xclip-copyfile file1 [sofie.homeip.net ~/doc]$ xclip-pastefile file1 [sofie.homeip.net ~/doc]$ cat file1 A file created on maggie.lkpg.cendio.se Copying an entire tree structure [sofie.homeip.net ~]$ xclip-copyfile doc [maggie.lkpg.cendio.se ~/tmp]$ xclip-pastefile doc/ doc/letter-mom-april.txt doc/file1 doc/letter-dad-march.txt Copying files with preserved path information [maggie.lkpg.cendio.se ~]$ xclip-copyfile -p /etc/sysconfig/grub tar: Removing leading `/' from member names [sofie.homeip.net ~/tmp]$ xclip-pastefile etc/sysconfig/grub [sofie.homeip.net ~/tmp]$ ls etc/sysconfig/grub etc/sysconfig/grub Moving files [sofie.homeip.net ~]$ ls letter-brother-may.txt letter-brother-may.txt [sofie.homeip.net ~]$ xclip-cutfile letter-brother-may.txt [sofie.homeip.net ~]$ ls letter-brother-may.txt ls: cannot access letter-brother-may.txt: No such file or directory [sofie.homeip.net ~]$ cd doc [sofie.homeip.net ~/doc]$ xclip-pastefile letter-brother-may.txt AUTHORS
This manual page was written by Maximilian Gass <mxey@cloudconnected.org> for the Debian project. It may be used for everything else, of course. XCLIP-COPYFILE(1)
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