Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: When does an if statement need parentheses
Top Forums Shell Programming and Scripting When does an if statement need parentheses Post 302546023 by Straitsfan on Wednesday 10th of August 2011 08:36:04 AM
Old 08-10-2011
When does an if statement need parentheses
I was looking at a script in my little book on bash and saw that one of the if statements had parentheses instead of brackets for the condition. I've been trying to find in my book where it talks about parentheses (because the examples on the if statement in an earlier chapter doesn't seem to mention them.

So I was wondering -- when are parentheses required for an if statement, and when are the brackets required? And could you tell me the syntax for the if statement when using parentheses?
 

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Parentheses in perl find/replace

I'm trying to use the following command to do a batch find and replace in all commonly named files through a file hierarchy find . -name 'file' |xargs perl -pi -e 's/find/replace/g' which works fine except for a substitution involving parenthesis. As a specific example I'm trying to sub... (3 Replies)
Discussion started by: Jeffish
3 Replies

2. Shell Programming and Scripting

Replace text in parentheses

Hi I would like to replace a comma in parentheses to a semicolon for example. Other commas outside () stay unchanged. How can I do this? aaaa,bbb,ccc,ddd(eee,fff,ggg),hhh,iii to aaaa,bbb,ccc,ddd(eee;fff;ggg),hhh,iii Thanks (5 Replies)
Discussion started by: lalelle
5 Replies

3. UNIX for Dummies Questions & Answers

brackets vs parentheses - single and double

hi, unix gurus. i am wondering if someone can give me a clear explanation of the differneces between parentheses and brackets, both single and double. i have heard that double parentheses (( are used for numerical expressions and that single brackets [ are used for strings. but i see... (1 Reply)
Discussion started by: ankimo
1 Replies

4. Shell Programming and Scripting

Perl regex help - matching parentheses

Let's say I'm trying to match potentially multiple sets of parentheses. Is there a way in a regular expression to force a match of closing parentheses specifically in the number of the opening parentheses? For example, if the string is "((foo bar))", I want to be able to say "match any number of... (7 Replies)
Discussion started by: cvp
7 Replies

5. UNIX for Dummies Questions & Answers

Brackets, parentheses in Shell Scripting

Hello, I have done a great deal of research on this and still cannot come to an understanding of the following: In if-else statements in shell scripting I have seen examples of single brackets, double brackets, single parantheses, and double paratheses. When should each one be used? And... (2 Replies)
Discussion started by: mojoman
2 Replies

6. UNIX for Dummies Questions & Answers

Replace all occurrences of strings with parentheses

Hi, I tried to adapt bartus's solution to my problem, without success. I want to replace all the occurences of this: with: , where something can contain an arbitrary number of balanced parens and brakets. Any ideas ? Best, (1 Reply)
Discussion started by: ff1969ff1969
1 Replies

7. Shell Programming and Scripting

Rules with using double parentheses in Bash

Hi.could you explain me what are the rules when we are using double parentesis in if statement,if I put ,the code is working ,with (( is not #!/bin/bash if (($# > 0)) then if ((! -d "$1")) then echo "Directory $1 not found" fi else echo Problem fi (8 Replies)
Discussion started by: lio123
8 Replies

8. Shell Programming and Scripting

Help with extracting data within parentheses

This is my input file: a|b|c(ef)|g|h(km)|p My output file should look like: a|b|ef|g|km|p That is, pipe is the delimiter. The data within pipe must be displayed as it is but if it encounters any data within parentheses, then only the data within parentheses has to be displayed ( the data... (2 Replies)
Discussion started by: ksatish89
2 Replies

9. Shell Programming and Scripting

[All variants] remove first pair of parentheses

How to remove first pair of parentheses and content in them from the beginning of the line? Here's the list: (ok)-test (ok)-test-(ing) (some)-test-(ing)-test test-(ing) Desired result: test test-(ing) test-(ing)-test test-(ing) Here's what I already tried with GNU sed: sed -e... (6 Replies)
Discussion started by: useretail
6 Replies

10. Answers to Frequently Asked Questions

Add string to parentheses

Suppose I have this code : int main () { int i = NULL; /* incorrect */ return 0; } and I want to put the word between the two parentheses like this : int main (void) { int i = NULL; /* incorrect */ return 0; } which command is used to do it in Linux ? (2 Replies)
Discussion started by: steve120
2 Replies

LEARN ABOUT DEBIAN

derivations

DERIVATIONS(7)						Derivations of Applied Mathematics					    DERIVATIONS(7)

NAME

       derivations - book: Derivations of Applied Mathematics

DESCRIPTION

       Understandably,	program sources rarely derive the mathematical formulas they use.  Not wishing to take the formulas on faith, a user might
       nevertheless reasonably wish to see such formulas somewhere derived.

       Derivations of Applied Mathematics is a book which documents and derives many of the mathematical formulas and methods implemented in  free
       software  or used in science and engineering generally.	It documents and derives the Taylor series (used to calculate trigonometrics), the
       Newton-Raphson method (used to calculate square roots), the Pythagorean theorem (used to calculate distances) and many others.

READING THE BOOK

       Among other ways, you can read the book on your computer screen by opening the file /usr/share/doc/derivations/derivations.ps.gz  with  the
       gv(1) program under X(7).  To print the book on a standard postscript printer, just zcat(1) then lpr(1) the same file.

FILES

       /usr/share/doc/derivations/derivations.ps.gz
	      the book in postscript format
       /usr/share/doc/derivations/derivations.pdf.gz
	      the book in PDF

BUGS

       The book is a work in progress.

AUTHOR

       The  book  and  this manpage are written by Thaddeus H. Black, who also maintains the Debian package derivations in which they are distrib-
       uted.  Users who need to contact the author in his role as Debian package maintainer can reach him at <thb@debian.org>.	However,  most	e-
       mail will naturally be about the book itself: this should be sent to <thb@derivations.org>.

COPYLEFT

       Copyright (C) 1983-2010 Thaddeus H. Black.

       The  book,  this manpage and the entire derivations distribution are free software.  You can redistribute them and/or modify them under the
       terms of the GNU General Public License, version 2.

SEE ALSO

       gv(1) [gv], zcat(1) [gzip], psselect(1) [psutils], lpr(1) [lpr], octave(1) [octave]

Thaddeus H. Black						   10 March 2010						    DERIVATIONS(7)
All times are GMT -4. The time now is 04:26 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy