Sponsored Content
Top Forums Shell Programming and Scripting ksh, difference between double bracket and single bracket Post 302584139 by BeefStu on Thursday 22nd of December 2011 09:24:57 AM
Old 12-22-2011
ksh, difference between double bracket and single bracket

Can somebody tell me the difference between double brackets and single
brackets, when doing a test.

I have always been acustomed to using single brackets and have not
encountered any issues to date. Why would somebody use double brackets.

Ie

Code:
 
if [[ "$a" = "$b ]]
 
vs
 
if [ "$a" = "$b" ]

Thanks to all who answer
 

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Extract string in square bracket

Hi Input text is some message some message some message Expected output is main value1 value2 value3 Any idea how to above values in square brackets using shell scripting? many thanks. (3 Replies)
Discussion started by: hnh
3 Replies

2. Shell Programming and Scripting

Best practice for bracket comparisons?

So, I have no formal higher education in programming at all and am self taught. I am now wondering what would be considered best practices? Like should I hard code a variable, then compare it to what I want to know or achieve, or should I just put the commands with in the brackets? Example, a... (5 Replies)
Discussion started by: tlarkin
5 Replies

3. Shell Programming and Scripting

Split a string with bracket

Hi, Am trying to split a string with bracket in ksh but it is not splitting it correctly. split("Hello, Name(1), Name(2)", main,","); How do i split correctly? (3 Replies)
Discussion started by: nightrider
3 Replies

4. Shell Programming and Scripting

extract word from bracket - shell

Related to : thread : 34769-removing-duplicate-lines-file.html i want to extract the words in () eg: string1="bla bla (aaa) aha hai (aa)" after processing output i need is : aaa aa (2 Replies)
Discussion started by: linuxadmin
2 Replies

5. Shell Programming and Scripting

Double bracket giving error

here is a small script I wrote: #! /bin/bash if ] then echo "argument is null" fi It is giving error: test.sh: any idea, why is it so? (2 Replies)
Discussion started by: vina201unx2011
2 Replies

6. Shell Programming and Scripting

Remove bracket part

Hi I have to remove in a file in first column whatever is written in brackets with brackets so one file hgfd 123 gfhdj 483 jdgfdg 34738 the output shuld be hgfd 123 gfhdj 483 jdgfdg 34738 (9 Replies)
Discussion started by: manigrover
9 Replies

7. Shell Programming and Scripting

variable inside if bracket

Is this possible? The below code not working for me. dir=mydir if ; then echo "found /home/$mydir " else echo "Not found /home/$mydir" fi ---------- Post updated at 05:28 AM ---------- Previous update was at 05:25 AM ---------- Its working for me now (1 Reply)
Discussion started by: anil510
1 Replies

8. Shell Programming and Scripting

Vim : Match all bracket { and fold them (zf%)

Hello ! I'm using a lot the command zf% with the cursor on the first bracket of a function for example, to fold it. Ex : I put my cursor on the first bracket myfunction(){ # body } I type zf% It become : +-- 9 lines : myfunction()... (2 Replies)
Discussion started by: Purgator
2 Replies

9. Shell Programming and Scripting

How to remove contents from file which are under bracket?

hello Friend, In hostgroup file, i have define lots of hostgroups. I need to remove few of them without manually editing file. Need script or syntax. I want to search particular on hostgroup_members and delete hostgoup defination of it. for example. define hostgroup{ hostgroup_name... (8 Replies)
Discussion started by: ghpradeep
8 Replies

10. UNIX for Beginners Questions & Answers

Error in ksh script: missing right bracket

I have no idea how to write ksh script, but i'm really in need of help with this. I using fedora 30 and in attempt of runnig attached script i getting those errors, i solved first error by removing excess bracket, but i do not know what should i do with other. Pls sorry for trash post. (8 Replies)
Discussion started by: NullPtr
8 Replies
test(1sh5)																test(1sh5)

Name
       test - condition evaluation command

Syntax
       test expr
       [ expr ]

Description
       The  command  evaluates the expression expr.  If the value of expr is true, the command returns a zero exit status; otherwise, it returns a
       nonzero exit status.  The command also returns a nonzero exit status if no arguments are specified.  The following primitives are  used	to
       construct expr:

       -r file	      True if file exists and is readable.

       -w file	      True if file exists and is writable.

       -x file	      True if file exists and is executable.

       -f file	      True if file exists and is a regular file.

       -d file	      True if file exists and is a directory.

       -c file	      True if file exists and is a character special file.

       -b file	      True if file exists and is a block special file.

       -p file	      True if file exists and is a named pipe (fifo).

       -u file	      True if file exists and its set-user-ID bit is set.

       -g file	      True if file exists and its set-group-ID bit is set.

       -k file	      True if file exists and its sticky bit is set.

       -s file	      True if file exists and has a size greater than zero.

       -t [ fildes ]  True if the open file whose file descriptor number is fildes (1 by default) is associated with a terminal device.

       -z s1	      True if the length of string s1 is zero.

       -n s1	      True if the length of the string s1 is non-zero.

       s1 = s2	      True if strings s1 and s2 are identical.

       s1 != s2       True if strings s1 and s2 are not identical.

       s1	      True if s1 is not the null string.

       n1 -eq n2      True  if	the integers n1 and n2 are algebraically equal.  Any of the comparisons -ne, -gt, -ge, -lt, and -le may be used in
		      place of -eq.

       These primitives can be combined with the following operators:

       !	      unary negation operator.

       -a	      binary and operator.

       -o	      binary or operator (-a has higher precedence than -o).

       ( expr )       parentheses for grouping.

       Note that all the operators and flags are separate arguments to the command.  Note also that parentheses are meaningful to  the	Shell  and
       must  be  escaped.   In the form of the command that uses square brackets ([]), instead of the word test, the brackets must be delimited by
       blanks.

See Also
       find(1), sh5(1), test(1)

																	test(1sh5)
All times are GMT -4. The time now is 05:56 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy