Maths in shell scripts


 
Thread Tools Search this Thread
Top Forums Shell Programming and Scripting Maths in shell scripts
# 1  
Old 01-11-2012
Maths in shell scripts

Hi,

Need help on this. I need to increment a variable by 1 but retain as 2 characters.

I am using expr to do additions:
Code:
NEWSERIAL=`expr $SERIAL + 1`

$SERIAL can range from 01-99. After adding "1", I need the result to be 2 characters, eg: 02+1 = 03. By default expr will truncate the zero such that 02+1 will become "3" not "03"

Please help. Much appreciated.

Thanks.

Last edited by Franklin52; 01-11-2012 at 07:24 AM.. Reason: Please use code tags for code and data samples, thank you
# 2  
Old 01-11-2012
one way ..
Code:
$ cnt=3
$ echo $cnt
3
$ [ $cnt -lt 10 ] && cnt=0$((cnt))
$ echo $cnt
03
$

# 3  
Old 01-11-2012
@jayan_jay: Wouldn't $cnt become 099, if [ $cnt -le 99 ] were in a loop incrementing $cnt by one each time?

@vchee: Try this.
Code:
NEWSERIAL=`printf "%02d" $(($SERIAL + 1))`

# 4  
Old 01-11-2012
Quote:
Originally Posted by balajesuri
@jayan_jay: Wouldn't $cnt become 099, if [ $cnt -le 99 ] were in a loop incrementing $cnt by one each time?

@vchee: Try this.
Code:
NEWSERIAL=`printf "%02d" $(($SERIAL + 1))`


Thanks for all the help. It works.
# 5  
Old 01-12-2012
@balaje, yes correct.. while using in loop it might get fail .. Thanks .. Smilie
Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Calculate the constant e to 14+ decimal places using integer maths.

Hi guys... I am loving this integer maths thing. 64 bit systems are certainly easier than 32 bit, but hey, I don't intend to leave out my fav' platform. Using one of the 'Brothers' methods, URL inside the code. #!/bin/sh # # #!/usr/local/bin/dash # e_constant.sh # Brother's formula . #... (2 Replies)
Discussion started by: wisecracker
2 Replies

2. Shell Programming and Scripting

Simple maths calculator loop.

Hi, I am trying to make a maths calculator that: 1. Prompts the user for a number. 2. Prompts the user for an operation (add, subtract, divide or multiply) 3. Prompts the user for a number. 4. Prompts the user for another operation (same as above) OR the option to get the result for the... (4 Replies)
Discussion started by: johnthebaptist
4 Replies

3. Shell Programming and Scripting

Using IF statements with maths where the input is not an integer

Hi All I've made a few scripts which using GDAL extract the value of a pixel within a given raster. The purpose is to work out the combine value of every pixel. I thought there may have been an easier way to do this but alas! The code below extracts the pixel value at position X Y. The... (3 Replies)
Discussion started by: StudentFitz
3 Replies

4. Shell Programming and Scripting

Maths with variables

Hello, I'm trying to write a while loop for a decimal value in tcsh which I know can't be done. Instead I want my increments to be one order of magnitude too large and then divide it by 10 when I use the variable. However, I don't know how to divide my variable and set it as another. set... (1 Reply)
Discussion started by: DFr0st
1 Replies

5. Shell Programming and Scripting

calling 'n' number of shell scripts based on dependency in one shell script.

Hello gurus, I have three korn shell script 3.1, 3.2, 3.3. I would like to call three shell script in one shell script. i m looking for something like this call 3.1; If 3.1 = "complete" then call 3.2; if 3.2 = ''COMPlete" then call 3.3; else exit The... (1 Reply)
Discussion started by: shashi369
1 Replies

6. Shell Programming and Scripting

Shell Scripts

deleted (1 Reply)
Discussion started by: zxc
1 Replies

7. Shell Programming and Scripting

Perl - maths equation - need help

if input to the perl program is ' ( p * ((a+b) * (c+d))) + q ' it shuld give the output as ' pac + pad + pbc + pbd + q ' .can anyone suggest a way to do this ? (7 Replies)
Discussion started by: Anuj8584
7 Replies

8. AIX

Difference between writing Unix Shell script and AIX Shell Scripts

Hi, Please give me the detailed Differences between writing Unix Shell script and AIX Shell Scripts. Thanks in advance..... (0 Replies)
Discussion started by: haroonec
0 Replies

9. Shell Programming and Scripting

Problem with Maths

Heres a script i wrote as a bit of practise. What it does is insert a line in the middle of a file. The line being $1 and the file being $2 #!/bin/bash rm tempfile touch tempfile count=1 linenum= `wc -l < $2` if then echo $1 >> $2 else even=`expr "$linenum" % 2` if then... (3 Replies)
Discussion started by: Quesa
3 Replies

10. Shell Programming and Scripting

shell scripts

Hi! I have added a line into /etc/profile which looks like- date > $HOME/.lastloggedon This puts a file lastloggedon into everyones directory who has logged in recently. The trouble I am having is getting the information back out. I was hoping there was a command using find which brought... (1 Reply)
Discussion started by: karenshaw
1 Replies
Login or Register to Ask a Question