Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: Faster than nested while read loops?
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!
 

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Grepping within nested for loops

Good morning - I have publication lists from 34 different faculty members. I need to end up with the numbers of publications in common across all 34 faculty. I need to grep person1 (last name) in list2, person1 in list3, person1 in list 4, etc., then person2 in list3, person 2 in list4, etc.,... (2 Replies)
Discussion started by: Peggy White
2 Replies

2. Shell Programming and Scripting

nested for loops

I need help getting over this bump on how nested for loops work in shell. Say i was comparing files in a directory in any other language my for loop would look like so for(int i=0;to then end; i++) for(int y = i+1; to the end; y++) I can't seem to understand how i can translate that... (5 Replies)
Discussion started by: taiL
5 Replies

3. Shell Programming and Scripting

Nested while loops (ksh scripting)

You can use one while inside another? I made the following script (without really knowing if I can use two while) to get 3 numbers different from each other at random: num1=$(( $RANDOM % 10 )) num2=$num1 while do num2=$(( $RANDOM % 10 )) done num3=$num1 while do while do... (1 Reply)
Discussion started by: ale.dle
1 Replies

4. Shell Programming and Scripting

Need help with Regular Expressions and nested loops

Ok... am going slightly loopy trying to get this working (no pun intended) What I need is to modify this code which takes a string input then echo's each character on a seperate line, to do the same thing but to put DIGIT: in front of numbers and LETTER: in front of letters. I know a regular... (5 Replies)
Discussion started by: U_C_Dispatj
5 Replies

5. Shell Programming and Scripting

KSH nested loops?

KSH isn't my strong suit but it's what my company has to offer. I've got a script with two nested loops, a FOR and UNTIL, and that works fine. When I add a CASE into the mix I end up getting "Unexpected 'done' at line xx" errors. Any suggestions on this? for divi in at ce ci cm co de di fl... (9 Replies)
Discussion started by: mrice
9 Replies

6. Shell Programming and Scripting

Nested for loops

Greetings All, The following script attempts to enumerate all users in all groups in the group file(GROUP) and echo the following information: GROUP ---> USER The script is as follows: IFS="," for GROUP in `ypcat -k group | cut -d" " -f1` do for USER in `ypcat -k group... (13 Replies)
Discussion started by: jacksolm
13 Replies

7. UNIX for Dummies Questions & Answers

Executing nested loops+foreach

It's been a while since I used csh formatting and I am having a little bit of trouble with a few things. Things seem so much easier to execute in Matlab, however I need to do this on the terminal because of the programs I am trying to interact with. So here's what I want to do: I have a file... (0 Replies)
Discussion started by: katia
0 Replies

8. Shell Programming and Scripting

two while nested loops

for server in $(echo `cat /tmp/ScanHosts_${USERSNAME}.TXT`) do for portnumber in $(echo `cat /tmp/ScanPorts_${USERSNAME}.TXT`) do #echo ${server} ${portnumber} ... (3 Replies)
Discussion started by: SkySmart
3 Replies

9. Shell Programming and Scripting

ksh - Need Help Reducing Nested Loops

Hello, I pulled out some old code from an unfinished project the other day and wanted to stream line it better. I know anything beyond a double loop is usually bad practice, and I came up with some logic for later that would no longer require the first loop in the following code that works: ... (5 Replies)
Discussion started by: Azrael
5 Replies

10. UNIX for Beginners Questions & Answers

Nested Loops for text file

Hi A text file containing data something likeVehicle: BMW Class checkin_note: Tyre : Four path_id : 11 vault_file_size: -1 Vehicle: Toyota Class checkin_note: Tyre : Four path_id : 11 vault_file_size: -1 Vehicle: Chevrolet Class checkin_note: Tyre : Five path_id :... (7 Replies)
Discussion started by: vipinHasija
7 Replies

LEARN ABOUT REDHAT

mac2unix

dos2unix(1)						      General Commands Manual						       dos2unix(1)

NAME

       dos2unix - DOS/MAC to UNIX text file format converter

SYNOPSYS

       dos2unix [options] [-c convmode] [-o file ...] [-n infile outfile ...]

       Options:

       [-hkqV] [--help] [--keepdate] [--quiet] [--version]

DESCRIPTION

       This manual page documents dos2unix, the program that converts plain text files in DOS/MAC format to UNIX format.

OPTIONS

       The following options are available:

       -h --help
	      Print online help.

       -k --keepdate
	      Keep the date stamp of output file same as input file.

       -q --quiet
	      Quiet mode. Suppress all warning and messages.

       -V --version
	      Prints version information.

       -c --convmode convmode
	      Sets conversion mode. Simulates dos2unix under SunOS.

       -o --oldfile file ...
	      Old file mode. Convert the file and write output to it. The program default to run in this mode. Wildcard names may be used.

       -n --newfile infile outfile ...
	      New  file  mode.	Convert the infile and write output to outfile. File names must be given in pairs and wildcard names should NOT be
	      used or you WILL lost your files.

EXAMPLES

       Get input from stdin and write output to stdout.

	      dos2unix

       Convert and replace a.txt. Convert and replace b.txt.

	      dos2unix a.txt b.txt

	      dos2unix -o a.txt b.txt

       Convert and replace a.txt in ASCII conversion mode.  Convert and replace b.txt in ISO conversion mode.  Convert	c.txt  from  Mac  to  Unix
       ascii format.

	      dos2unix a.txt -c iso b.txt

	      dos2unix -c ascii a.txt -c iso b.txt

	      dos2unix -c mac a.txt b.txt

       Convert and replace a.txt while keeping original date stamp.

	      dos2unix -k a.txt

	      dos2unix -k -o a.txt

       Convert a.txt and write to e.txt.

	      dos2unix -n a.txt e.txt

       Convert a.txt and write to e.txt, keep date stamp of e.txt same as a.txt.

	      dos2unix -k -n a.txt e.txt

       Convert and replace a.txt. Convert b.txt and write to e.txt.

	      dos2unix a.txt -n b.txt e.txt

	      dos2unix -o a.txt -n b.txt e.txt

       Convert c.txt and write to e.txt. Convert and replace a.txt.  Convert and replace b.txt. Convert d.txt and write to f.txt.

	      dos2unix -n c.txt e.txt -o a.txt b.txt -n d.txt f.txt

DIAGNOSTICS

BUGS

       The program does not work properly under MSDOS in stdio processing mode.  If you know why is that so, please tell me.

AUTHORS

       Benjamin Lin - <blin@socs.uts.edu.au>

       Bernd Johannes Wuebben (mac2unix mode) <wuebben@kde.org>

MISCELLANY

       Tested environment:

	      Linux 1.2.0 with GNU C 2.5.8

	      SunOS 4.1.3 with GNU C 2.6.3

	      MS-DOS 6.20 with Borland C++ 4.02

       Suggestions and bug reports are welcome.

SEE ALSO

       unix2dos(1) mac2unix(1)

1995.03.31							   dos2unix v3.0						       dos2unix(1)
All times are GMT -4. The time now is 07:42 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy