Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: Issues with 'expr'
Top Forums UNIX for Dummies Questions & Answers Issues with 'expr' Post 302791117 by Don Cragun on Monday 8th of April 2013 02:31:26 AM
Old 04-08-2013
Quote:
Originally Posted by akarnya
Hi,

I have a text file where i define all the inputs to my shell script:
IP=1.2.3.4
PC=1234

In the shell script, i am trying to read the input variables from the above mentioned text file:

#!/bin/bash
#usage
IP=expr cat /tmp/input.txt | grep IP| cut -d "=" -f2
PC=expr cat /tmp/input.txt | grep PC | cut -d "=" -f2

echo "machine=$IP, PC=$PC"

But, i am getting the output as machine= , PC=

The correct values are not displayed
I'm very surprised that you didn't get diagnostic messages from your shell pointing out that expr cat /tmp/input.txt is a syntax error; the expr utility does not have a cat operator.
Change:
Code:
IP=expr cat /tmp/input.txt | grep IP| cut -d "=" -f2
PC=expr cat /tmp/input.txt | grep PC | cut -d "=" -f2

to:
Code:
. /tmp/input.txt

 

10 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers

expr

Hello! I want to evaluate some mathematical expressions in a script and I try to use 'expr' command. Unfortunatally, when I have, for example, expr 8.2 + 6 the result is 'expr: non-numeric argument' Why ? I work on SunOs 5.7. Thanks in advance Nathe (5 Replies)
Discussion started by: Nathe
5 Replies

2. Red Hat

how to use expr

i am new to shell programming, currently using redhat linux of version 2.4.20-8. i have problem in executing expr command in the following shell script $ x=5 $ x='expr $x + 1' $ echo $x the output is displaying always expr $x + 1 Pls guide me for the above query (3 Replies)
Discussion started by: saikumarm80
3 Replies

3. Shell Programming and Scripting

Expr issues

I have two variables that are set by a number i.e. recs_on_db=12 yesterdays_recs_on_db=10 i need to get the difference between the two and be able to set this in a variable I have tried expr but does not work: db_difference=`expr $recs_on_db - $yesterdays_recs_on_db` i get: expr:... (2 Replies)
Discussion started by: Pablo_beezo
2 Replies

4. Shell Programming and Scripting

test expr VS [ expr ]

What is the difference between test expr VS . For example : if test 5 -eq 6 echo "Wrong" and if echo "Wrong" bot will give the same output as Wrong. Now, what is the difference between these two? though they are producing the same result why we need two? Any answer will be... (2 Replies)
Discussion started by: ashok.g
2 Replies

5. Shell Programming and Scripting

Issues with expr command on Solaris Box

Hello Friends, I have written a code on a Linux box, however, am getting issues while running it on a Solaris server. The issue with Sed command is sortd out, however, am still lokking for solutions with expr command. Here is the issue, Linux : bash-2.03$ expr match singh@test.com... (10 Replies)
Discussion started by: suffisandy
10 Replies

6. Shell Programming and Scripting

the expr \*

$ cat > mtable #!/bin/sh # #Script to test for loop # # if then echo "Error - Number missing form command line argument" echo "Syntax : $0 number" echo "Use to print multiplication table for given number" exit 1 fi n=$1 for i in 1 2 3 4 5 6 7 8 9 10 do echo "$n * $i = `expr $i \*... (1 Reply)
Discussion started by: jackel7777
1 Replies

7. UNIX for Dummies Questions & Answers

expr ?!

Hey there i want to subtract the content from $b from $a. Each variable has got 18 values (normal numbers from 0 - 99). How can i subtract them? I know i have to use the expr command, this is what i have till now: a=`cat Tabelle.dat | awk {'print $4'} | awk -F: {'print $1'}` b=`cat... (1 Reply)
Discussion started by: Mad van Bert
1 Replies

8. Shell Programming and Scripting

Error with expr - "expr: syntax error"

Hi All, I'm writing a shell script in KSH, where I want to store the filename, total record count and actual record count of all the source files. The source files reside in 4 different sub-folders under the same root folder. Below is code: #!/usr/bin/ksh... (6 Replies)
Discussion started by: jagari
6 Replies

9. Shell Programming and Scripting

If + expr

Hi I have bellow script: t1=`cat node1.txt | grep thread1 | cut -f2 -d '-'` t2=`cat node2.txt | grep thread2 | cut -f2 -d '-'` t3=`cat node1_rcat.txt | grep thread1 | cut -f2 -d '-'` t4=`cat node2_rcat.txt | grep thread2 | cut -f2 -d '-'` if ]; then echo "no restore" >> log.log... (6 Replies)
Discussion started by: primo102
6 Replies

10. Shell Programming and Scripting

Nn$( expr $n + 1)

HI there I am trying to understand Shell scripting to create my own, I am attempting a few examples can anyone tell me what this means?n=$( expr $n + 1)Tried looking on the internet, but just cannot find its anywhere :( .Help please (4 Replies)
Discussion started by: steve2015
4 Replies

LEARN ABOUT DEBIAN

bup-margin

bup-margin(1)						      General Commands Manual						     bup-margin(1)

NAME

       bup-margin - figure out your deduplication safety margin

SYNOPSIS

       bup margin [options...]

DESCRIPTION

       bup margin  iterates  through  all  objects  in	your  bup repository, calculating the largest number of prefix bits shared between any two
       entries.  This number, n, identifies the longest subset of SHA-1 you could use and still encounter a collision between your object ids.

       For example, one system that was tested had a collection of 11 million objects (70 GB), and bup margin returned 45.  That  means  a  46-bit
       hash  would be sufficient to avoid all collisions among that set of objects; each object in that repository could be uniquely identified by
       its first 46 bits.

       The number of bits needed seems to increase by about 1 or 2 for every doubling of the number of objects.  Since SHA-1 hashes have 160 bits,
       that  leaves 115 bits of margin.  Of course, because SHA-1 hashes are essentially random, it's theoretically possible to use many more bits
       with far fewer objects.

       If you're paranoid about the possibility of SHA-1 collisions, you can monitor your repository by running bup margin occasionally to see	if
       you're getting dangerously close to 160 bits.

OPTIONS

       --predict
	      Guess  the offset into each index file where a particular object will appear, and report the maximum deviation of the correct answer
	      from the guess.  This is potentially useful for tuning an interpolation search algorithm.

       --ignore-midx
	      don't use .midx files, use only .idx files.  This is only really useful when used with --predict.

EXAMPLE

	      $ bup margin
	      Reading indexes: 100.00% (1612581/1612581), done.
	      40
	      40 matching prefix bits
	      1.94 bits per doubling
	      120 bits (61.86 doublings) remaining
	      4.19338e+18 times larger is possible

	      Everyone on earth could have 625878182 data sets
	      like yours, all in one repository, and we would
	      expect 1 object collision.

	      $ bup margin --predict
	      PackIdxList: using 1 index.
	      Reading indexes: 100.00% (1612581/1612581), done.
	      915 of 1612581 (0.057%)

SEE ALSO

       bup-midx(1), bup-save(1)

BUP

       Part of the bup(1) suite.

AUTHORS

       Avery Pennarun <apenwarr@gmail.com>.

Bup unknown-															     bup-margin(1)
All times are GMT -4. The time now is 03:27 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy