A $(( expression )) bug? Post: 302982348

Sponsored Content

Top Forums UNIX for Advanced & Expert Users A $(( expression )) bug? Post 302982348 by wisecracker on Wednesday 28th of September 2016 09:07:20 AM

09-28-2016

Registered User

Quote:

Originally Posted by Don Cragun

In an arithmetic evaluation, the value of a variable can be specified by expanding the variable (i.e. $var or ${var}) or by just giving the variable name (i.e. var). But the expression that is the numeric evaluation of the length of the string that is the value of a variable must use the expansion of the variable that produces that number (i.e. ${#var}); you cannot skip the ${ and } when you are using shell variable expansion operators like ${#var} or ${var%%pattern} or ${var:offset:length}.

OK, I'll go with that BUT, and a big but, why does Shell Check echo "$(( #txt - 1 ))" NOT come up with a syntax error knowing from the various scenarios that it does?
Should there not be a warning saying so. Note that in the Shell Check example I was using the worst case sh . Tested on the others gave errors or incorrect results too.
On reading RudiC's post it looks as though it SHOULD work but obviously it doesn't, or I am misinterpreting it?
Anyhow thanks, but I will keep '$/${}' in all cases just to be on the safe side.

wisecracker

View Public Profile for wisecracker

Find all posts by wisecracker

8 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Regular Expression + Aritmetical Expression

Is it possible to combine a regular expression with a aritmetical expression? For example, taking a 8-numbers caracter sequece and casting each output of a grep, comparing to a constant. THX!

2. Programming

error: initializer expression list treated as compound expression

I had seen this error for the first time ..... error: initializer expression list treated as compound expression please help....

3. AIX

bug in 43 ???

xxxxserver# lsattr -El inet0 | grep 255.240.0.0,32.224.0.0,32.78.120.254 | grep '.40' route net,-hopcount,1,-netmask,255.240.0.0,32.224.0.0,32.78.120.254 How this is possible?

4. UNIX for Dummies Questions & Answers

where's the bug?

#!/bin/bash if then #echo "infinite loop" exit 0 fi when I run this file I get the following error: ./test_infinite_loop: line 5: syntax error near unexpected token `fi' ./test_infinite_loop: line 5: `fi' :confused:

5. Shell Programming and Scripting

Integer expression expected: with regular expression

CA_RELEASE has a value of 6. I need to check if that this is a numeric value. if not error. source $CA_VERSION_DATA if * ] then echo "CA_RELESE $CA_RELEASE is invalid" exit -1 fi + source /etc/ncgl/ca_version_data ++ CA_PRODUCT_ID=samxts ++ CA_RELEASE=6 ++ CA_WEEK_NO=7 ++...

6. Programming

Perl: How to read from a file, do regular expression and then replace the found regular expression

Hi all, How am I read a file, find the match regular expression and overwrite to the same files. open DESTINATION_FILE, "<tmptravl.dat" or die "tmptravl.dat"; open NEW_DESTINATION_FILE, ">new_tmptravl.dat" or die "new_tmptravl.dat"; while (<DESTINATION_FILE>) { # print...

7. UNIX for Advanced & Expert Users

sed: -e expression #1, char 0: no previous regular expression

Hello All, I'm trying to extract the lines between two consecutive elements of an array from a file. My array looks like: problem_arr=(PRS111 PRS213 PRS234) j=0 while } ] do k=`expr $j + 1` sed -n "/${problem_arr}/,/${problem_arr}/p" problemid.txt ---some operation goes...

8. Shell Programming and Scripting

Why Relational Expression is Writing to a Expression?

Hello All, Not sure why this is happening... When the following If Statement is evaluated for some reason it is creating a file in the CWD called '0'. I've seen this happen before, just not in an If Statement... CODE: if then DIR_NAME="$1" DIR_SIZE=0 STATUS="" else...

LEARN ABOUT CENTOS

grub-render-label

GRUB-RENDER-LABEL(1)                                               User Commands                                              GRUB-RENDER-LABEL(1)

NAME

       grub-render-label - generate a .disk_label for Apple Macs.

SYNOPSIS

       grub-render-label [OPTION...] [OPTIONS]

DESCRIPTION

       Render Apple .disk_label.

       -b, --bgcolor=COLOR
              use COLOR for background

       -c, --color=COLOR
              use COLOR for text

       -f, --font=FILE
              use FILE as font (PF2).

       -i, --input=FILE
              read text from FILE.

       -o, --output=FILE
              set output filename. Default is STDOUT

       -t, --text=STRING
              set the label to render

       -v, --verbose
              print verbose messages.

       -?, --help
              give this help list

       --usage
              give a short usage message

       -V, --version
              print program version

       Mandatory or optional arguments to long options are also mandatory or optional for any corresponding short options.

REPORTING BUGS

       Report bugs to <bug-grub@gnu.org>.

SEE ALSO

       The  full  documentation  for grub-render-label is maintained as a Texinfo manual.  If the info and grub-render-label programs are properly
       installed at your site, the command

              info grub-render-label

       should give you access to the complete manual.

grub-render-label (GRUB) 2.02-2ubuntu8.3                             July 2018                                                GRUB-RENDER-LABEL(1)