Sponsored Content
Top Forums UNIX for Dummies Questions & Answers Need help with repeating variables in a shell script Post 302760723 by bakunin on Thursday 24th of January 2013 01:27:38 PM
Old 01-24-2013
There are a few problems with your script, conceptually and otherwise. The bottom line - to spare you the effort of IMHO optimizing a hopeless case - is that this problem is IMHO suited to a high-level language (C, whatever - pick any).

First, the shells input function is based on the terminal handling of Unix and therefore not suited to the way you want to treat the input: basically a Unix terminal is a file, where you can read from (input) and write to (output). What's more Unix was historically designed as a multi-user system. One system at the center and a number (typically a dozen or two) terminals connected to it. The Unix terminal deals with lines of data: a "read" statement will take any amount of keystrokes but only process them once the user hits <ENTER>. This is so because this way the central system will have to pay only very limited attention to the terminal until the user does formally end his input. The system is similar to how IBM mainframes deal with their terminals and the reason why they can handle vast amounts of sessions at the same time with comparatively limited resources. Would the system have to pay attention to every keystroke it would do nothing else than paying attention as the number of sessions increases.

What you now want is to indeed pay attention to every keystroke. The shell is - because of historical reasons given above - not designed to do so.

Apart from the conceptual problem there are only very minor problems which usually happen to beginners. In fact you have done astonishingly well for a beginner:

Code:
old_tty_settings=`stty -g`

You use this device (the backticks) several times. Backticks are deprecated and only support for backwards compatibility. Instead of backticks use "$(..)":

Code:
old_tty_settings="$(stty -g)"

Then you don't pay attention to quoting:

Code:
fullstring=$char00$char01$char02$char03$char04$char05

This is not a high-level-language. The shell interpretes this line by replacing the variables with their content in a first pass, then executing what results in another pass (there are actually several passes, but these two matter in this case). To protect your variables content from being interpreted by the shell you should always quote them:

Code:
fullstring="$char00$char01$char02$char03$char04$char05"

For the same reason i quoted to subshell call with which i replaced the backticks before. This way you are always on the safe side. Only omit the quotes for the expressed purpose of having the string interpreted by the shell.

Last is you don't pay attention to the variable scope. Where is "grabbed_char" belonging to? Even if the shell allows you to introduce variables on the fly you should work like it doesn't, simply because this way you get more orer in your source and have less maintenance effort in the future.

You should define a variable (use "typeset") in the main program and then pass the output via <stdin>. The following sketch shows the mechanism:

Code:
#! /bin/bash

sub_function ()
{
     typeset argument="$1"
     echo "a $argument"
     return 0
}

# main ()
typeset string1=""
typeset string2=""

string1=$(sub_function "foo")"; echo "$string1"
string2=$(sub_function "bar")"; echo "$string2"

exit 0

I hope this helps.

bakunin
 

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Shell Script Variables

HI guys I need to store the output of a sql query in a variable, can you tell me how to do that eg) select count(*) from s_escl_req $count = count(*) from s_escl_req how would i store the count(*) from the sql statement in a variable called $count. thanks (3 Replies)
Discussion started by: ragha81
3 Replies

2. Shell Programming and Scripting

Repeating variables in the code

Hi all, I had written 3 KSH scripts for different functionalities. In all these 3 files there are some 30 variables in common. So I want to reduce the code by placing these variables in a common properties file named (dataload.prop/dataload.parms/dataload.txt) or txt file and access it... (1 Reply)
Discussion started by: mahalakshmi
1 Replies

3. Shell Programming and Scripting

Accessing variables of one shell script in another shell script

I have a variable $exe in a shell script file a.sh which I need to access in another shell script file b.sh. How can I do that? :rolleyes: Thanks!! (2 Replies)
Discussion started by: looza
2 Replies

4. Shell Programming and Scripting

Accessing variables of one shell script in another shell script

Hi All, I have a shell script called sample1.sh where I have 2 variables. Now I have another shell script called sample2.sh. I want the variables in sample1.sh to be available to sample2.sh. For example. In sample1.sh I am finding the sum of 2 numbers namely a and b. Now I want to access... (2 Replies)
Discussion started by: rsendhilmani
2 Replies

5. Shell Programming and Scripting

Variables in shell script

mysqldump --compact --add-drop-table -h192.168.150.80 -uroot -p somePass $combined | sed '/$combined/$table/g' | mysql $databaseThe sed part is not working from the above statement. The variables combined and table are already defined and instead of showing the actual variable, it is executing the... (4 Replies)
Discussion started by: shantanuo
4 Replies

6. Shell Programming and Scripting

Shell script to extract data in repeating tags from xml

Hi, I am new to shell scripting. I need to extract data between repeating tags from an xml file and store the data in an array to process it further. <ns1:root xmlns:ns1="http://example.com/config"> <ns1:interface>in1</ns1:interface> <ns1:operation attribute1="true" attribute2="abd"... (2 Replies)
Discussion started by: sailendra
2 Replies

7. UNIX for Dummies Questions & Answers

Adding variables to repeating strings

Hello, I want to add a letter to the end of a string if it repeats in a column. so if I have a file like this: DOG001 DOG0023 DOG004 DOG001 DOG0023 DOG001 the output should look like this: DOG001-a DOG0023-a DOG004 DOG001-b (15 Replies)
Discussion started by: verse123
15 Replies

8. UNIX for Dummies Questions & Answers

How to write Config shell script to pass variables in master shell script?

Dear Unix gurus, We have a config shell script file which has 30 variables which needs to be passed to master unix shell script that invokes oracle database sessions. So those 30 variables need to go through the database sessions (They are inputs) via a shell script. one of the variable name... (1 Reply)
Discussion started by: dba1981
1 Replies

9. Shell Programming and Scripting

How to write config shell script to pass variables in master shell script?

Dear Unix gurus, We have a config shell script file which has 30 variables which needs to be passed to master unix shell script that invokes oracle database sessions. So those 30 variables need to go through the database sessions (They are inputs) via a shell script. one of the variable name... (1 Reply)
Discussion started by: dba1981
1 Replies

10. Shell Programming and Scripting

Shell script to create runtime variables based on the number of parameters passed in the script

Hi All, I have a script which intends to create as many variables at runtime, as the number of parameters passed to it. The script needs to save these parameter values in the variables created and print them abc.sh ---------- export Numbr_Parms=$# export a=1 while do export... (3 Replies)
Discussion started by: dev.devil.1983
3 Replies
All times are GMT -4. The time now is 02:02 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy