Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: awk problem
Special Forums UNIX Desktop Questions & Answers awk problem Post 302534807 by agama on Tuesday 28th of June 2011 09:12:44 PM
Old 06-28-2011
In Korn Shell and bash, the constructs if [[ expression ]] and if (( expression )) are interpreted by the shell. The if [ expression ] is actually a command that the shell executes; the '[' is the command name.

The first noticeable difference is the overhead that the '[' command requires as a new process must be started, the binary loaded, and then cleaned up all to evaluate the expression to determine true or false. If you don't need to use the single bracket command, it is much more efficient to use the built-in evaluation.

Something that isn't obvious is that Kshell treats the right hand side of the expression as a pattern; the test (or [ command) does not. This allows you to do something like this:

Code:
if  [[  $var_name == *"foo"* ]]

Bash might do this too; I'm not a heavy bash user so I don't know for sure.

The (( expression )) is meant for numerical expressions while the double bracketed version is meant for string expressions. While this is still supported:

Code:
if [[ $var -gt 10 ]]

Kshell will give a warning (when run with -n) that it is obsolete. This would be the preferred syntax:

Code:
if (( $var > 10 ))

I hope this has answered your question.
This User Gave Thanks to agama For This Post:
mrbinoy
 

10 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers

AWK Problem

Hi, I posted something here about this yesterday but I can't seem to find it. I needed help writting a script which would append a file with new lines after every so many charachters. Example: (my original flat file) L60 LETTER OF CREDIT 60 DAYS W00 ON RECEIPT WIRE TRANSFER W30 NET... (12 Replies)
Discussion started by: gseyforth
12 Replies

2. Shell Programming and Scripting

Problem with AWK

Hi All, How can i store a value of the unix command executed in AWK with system command. devise=`cut -c1-3 dvgp.txt` I wrote this command in awk as awk'{ code= sprintf("devise=`cut -c1-3 dvgp.txt`"); system(code); }' Is this correct. can you please suggest me how the code can be... (1 Reply)
Discussion started by: krishna_gnv
1 Replies

3. Shell Programming and Scripting

problem using awk

Hi there every body I'm new to shell scripting and there is a problem facing me,, please look at the following piece of code: awk ' BEGIN{ FS="<assertion id=\1"; RS="<assertion id=\"2"}/<assertion id=\"1/{print FS$2 > "/home/ds2/test/output.txt"} ' filename all I wanna do is to... (6 Replies)
Discussion started by: senior_ahmed
6 Replies

4. Shell Programming and Scripting

Awk problem: How to express the single quote(') by using awk print function

Actually I got a list of file end with *.txt I want to use the same command apply to all the *.txt Thus I try to find out the fastest way to write those same command in a script and then want to let them run automatics. For example: I got the file below: file1.txt file2.txt file3.txt... (4 Replies)
Discussion started by: patrick87
4 Replies

5. Shell Programming and Scripting

Problem with awk awk: program limit exceeded: sprintf buffer size=1020

Hi I have many problems with a script. I have a script that formats a text file but always prints the same error when i try to execute it The code is that: { if (NF==17){ print $0 }else{ fields=NF; all=$0; while... (2 Replies)
Discussion started by: fate
2 Replies

6. Shell Programming and Scripting

awk problem

Find the number of files with sizes > 100KB in /, /bin, /usr, /usr/bin and /usr/sbin directories and output them in a two column format with the name of the directory and the number of files. i tried with awk $>ls -lh | awk '/^-/ && $5 >= 100k {print $8 $5}' but it is not working pls tell... (3 Replies)
Discussion started by: abhikamune
3 Replies

7. UNIX for Dummies Questions & Answers

Little problem with AWK

I thought I had solved this problem but after testing the script I came to realize that it is not doing what I need. So, here it goes again. This is the code: awk '/\>/{F=$2; N=$3; split(FILENAME, A, "."); getline; x = ">"}{print ">" A"-" x++" "F" " N"\n" $0}' This is the input file: ... (5 Replies)
Discussion started by: Xterra
5 Replies

8. Shell Programming and Scripting

awk problem - combining awk statements

i have a datafile that has several lines that look like this: 2,dataflow,Sun Mar 17 16:50:01 2013,1363539001,2990,excelsheet,660,mortar,660,4 using the following command: awk -F, '{$3=strftime("%a %b %d %T %Y,%s",$3)}1' OFS=, $DATAFILE | egrep -v "\-OLDISSUES," | ${AWK} "/${MONTH} ${DAY}... (7 Replies)
Discussion started by: SkySmart
7 Replies

9. Shell Programming and Scripting

awk problem

i have an email list in file.txt with comma separated line1 - FIELD1,pippo@gmail.com,darth@gmail.com line2 - FIELD2,pippo@gmail.com,darth@gmail.com,sampei@gmail.com output=(awk -F ',' -v var="$awkvar" '$1==var {print $2,$3,$4}' spreadsheet.txt)but awk delete some letters at the... (8 Replies)
Discussion started by: pasaico
8 Replies

10. Shell Programming and Scripting

awk problem

Hi I have two columns and I would like to create a third column based on how many lines away from a value of 1 in column 2, for example I have 1,0 2,0 3,0 4,0 5,0 6,1 7,0 8,0 9,0 10,0 11,1 And I want an output (6 Replies)
Discussion started by: garethsays
6 Replies

LEARN ABOUT MINIX

let

let(1)                                                             User Commands                                                            let(1)

NAME

       let - shell built-in function to evaluate one or more arithmetic expressions

SYNOPSIS

   ksh
       let arg...

DESCRIPTION

   ksh
       Each arg is a separate "arithmetic expression" to be evaluated.

EXIT STATUS

       The following exit values are returned:

       0        The value of the last expression is non-zero.

       1        The value of the last expression is zero.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE         |      ATTRIBUTE VALUE        |
       +-----------------------------+-----------------------------+
       |Availability                 |SUNWcsu                      |
       +-----------------------------+-----------------------------+

SEE ALSO

       ksh(1), set(1), typeset(1), attributes(5)

SunOS 5.10                                                          15 Apr 1994                                                             let(1)
All times are GMT -4. The time now is 08:02 PM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy