Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: bash and ksh: variable lost in loop in bash?
Top Forums Shell Programming and Scripting bash and ksh: variable lost in loop in bash? Post 302228796 by estienne on Monday 25th of August 2008 12:47:01 PM
Old 08-25-2008
bash and ksh: variable lost in loop in bash?
Hi,

I use AIX (ksh) and Linux (bash) servers. I'm trying to do scripts to will run in both ksh and bash, and most of the time it works. But this time I don't get it in bash (I'm more familar in ksh).

The goal of my script if to read a "config file" (like "ini" file), and make various report. I really simplified my script and reproduce the problem. It seems that variable inside "while loop" are lost in bash, but not in ksh?

Here's the script:

#!/bin/bash

function read_configfile
{
typeset configfile="$1"
typeset Hostname="$2"

grep '=' $configfile | sed "s/'//g" | while read ligne; do
variable="$(echo "$ligne" | awk -F= '{print $1}')"
value="$(echo "$ligne" awk -F= '{print $2}')"
eval "$variable='$value'"
done

echo "Affectation=$Affectation"
}

read_configfile bogus.in $(hostname)


And the bogus.in file:

Affectation=Yes life is good

When run, the output is

Affectation=

So... First of all I want to understand WHY the behavior is different. Is it because the way the "pipe" are processed?

Second, I found a way to bypass this. I just put every "variable=value" in a file (echo equation >>file), and outside the loop I'm doing an eval, and it works. But I would prefer NOT to use temporary file, so if you have any suggestions...

Thanks.
Last edited by estienne; 08-25-2008 at 01:55 PM..
 

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

bash & Ksh loop problem

hi i was trying to optimize one script and i came across this problem .. i am putting some pseudo code here $ >cat a.sh ls | while read I do i=$(($i + 1)) done echo "total no of files : " $ >ksh a.sh total no of files : $ >bash a.sh total no of files : why is... (1 Reply)
Discussion started by: zedex
1 Replies

2. Shell Programming and Scripting

Emulate ksh's FPATH variable in bash

Over time i have developed a library of useful (ksh) functions which i use in most of my scripts. I use the ksh's FPATH variable to locate all these functions and use a standard environment-setting-function to always have the same environment in all my scripts. Here is how i begin scripts: ... (3 Replies)
Discussion started by: bakunin
3 Replies

3. Shell Programming and Scripting

(BASH) Using a loop variable to grep something in a file?

Hi, I have a loop running until a variable L that is read previously in the full script. I'd like to grep some information in an input file at a line that contains the value of the loop parameter $i. I've tried to use grep, but the problem is nothing is written in the FILE files. It seems grep... (5 Replies)
Discussion started by: DMini
5 Replies

4. UNIX for Dummies Questions & Answers

Help with 3 variable bash loop

Hi all! I think someone might be able to solve my problem pretty easily. I am trying to run a bash loop with 3 variables. I know how to do: for var1 in `cat list1`; do for var2 in `cat list2`; do for var3 in `cat list3`; command var1 var2 > var3; done; done; done However, this will run all... (4 Replies)
Discussion started by: torchij
4 Replies

5. Programming

Global variable in for loop (BASH)

Hello, I'm trying to read the variable "pause" from a for loop without luck. The function is dependant on the outcome of the test within the loop. If i run this, pause is always 0 within the function. Any ideas? Thanks. pause=0 users=1 (for (( ; ; )) do speed=`cat speed.log` ... (7 Replies)
Discussion started by: shadyuk
7 Replies

6. Shell Programming and Scripting

Bash for loop with arrays second variable?

I am fairly new to bash and am not sure how to resolve this: I have a series of geographical long/lat points eg. 50/-30 listed on separate lines in a file called junk2. I have input these into an array and am then using that array in a for loop. Towards the end of the loop I create a file called... (4 Replies)
Discussion started by: lily-anne
4 Replies

7. Shell Programming and Scripting

Variable scop ksh vs bash

I am not clear why the cnt variable is not increased in the script below: #!/bin/bash INPF=${1:-a.txt}; KWDS=${2:-lst} cnt=0; grep -v '^#' $KWDS | while read kwd; do grep -q $kwd $INPF; if ; then echo Found; ((cnt=cnt+1)); fi... (5 Replies)
Discussion started by: migurus
5 Replies

8. Shell Programming and Scripting

Bash variable available for use outside loop

In the below for loop, I extract a variable $d which is an id that will change each time. The bash executes the problem that I am having is that p (after the done) is the path with the extracted $d. However, I can not use it in subsequent loops as it is not reconized. I have been trying to change... (3 Replies)
Discussion started by: cmccabe
3 Replies

9. UNIX for Beginners Questions & Answers

How do I assign the output of a command to a variable within a loop in bash?

In the else of the main if condition . else set lnk = $(readlink -f <path> | cut -d '/' -f7) echo "$lnk" if ] When I run the above on command line , the execution seems to be fine and I get the desired output. But when I try to assign it to a variable within a loop... (12 Replies)
Discussion started by: sankasu
12 Replies

10. UNIX for Beginners Questions & Answers

Bash Variable scope - while loop while reading from a file

Cope sample1: test.sh i=0 echo " Outside loop i = $i " while do i=$(( $i + 1)) echo "Inside loop i = $i " done echo " Out of loop i is : $i " When run output : Outside loop i = 0 Inside loop i = 1 Inside loop i = 2 Inside loop i = 3 Inside loop i = 4 Inside loop i = 5 Inside... (8 Replies)
Discussion started by: Adarshreddy01
8 Replies

LEARN ABOUT MINIX

shell_builtins

shell_builtins(1)                                                                                                                shell_builtins(1)

NAME

       shell_builtins, case, for, foreach, function, if, repeat, select, switch, until, while - shell command interpreter built-in commands

       The  shell  command  interpreters  csh(1), ksh(1), and sh(1) have special built-in commands. The commands case, for, foreach, function, if,
       repeat, select, switch, until, and while are commands in the syntax recognized by the shells. They are described in the Commands section of
       the  manual  pages of the respective shells. The remaining commands listed in the table below are built into the shells for reasons such as
       efficiency or data sharing between command invocations. They are described on their respective manual pages.

                                    |
                 Command            |           Shell
       alias                        |csh, ksh
       bg                           |csh, ksh, sh
       break                        |csh, ksh, sh
       case                         |csh, ksh, sh
       cd                           |csh, ksh, sh
       chdir                        |csh, sh
       continue                     |csh, ksh, sh
       dirs                         |csh
       echo                         |csh, ksh, sh
       eval                         |csh, ksh, sh
       exec                         |csh, ksh, sh
       exit                         |csh, ksh, sh
       export                       |ksh, sh
       false                        |ksh
       fc                           |ksh
       fg                           |csh, ksh, sh
       for                          |ksh, sh
       foreach                      |csh
       function                     |ksh
       getopts                      |ksh, sh
       glob                         |csh
       goto                         |csh
       hash                         |ksh, sh
       hashstat                     |csh
       history                      |csh
       if                           |csh, ksh, sh
       jobs                         |csh, ksh, sh
       kill                         |csh, ksh, sh
       let                          |ksh
       limit                        |csh
       login                        |csh, ksh, sh
       logout                       |csh, ksh, sh
       nice                         |csh
       newgrp                       |ksh, sh
       nohup                        |csh
       notify                       |csh
       onintr                       |csh
       popd                         |csh
       print                        |ksh
       pushd                        |csh
       pwd                          |ksh, sh
       read                         |ksh, sh
       readonly                     |ksh, sh
       rehash                       |csh
       repeat                       |csh
       return                       |ksh, sh
       select                       |ksh
       set                          |csh, ksh, sh
       setenv                       |csh
       shift                        |csh, ksh, sh

       source                       |csh
       stop                         |csh, ksh, sh
       suspend                      |csh, ksh, sh
       switch                       |csh
       test                         |ksh, sh
       time                         |csh
       times                        |ksh, sh
       trap                         |ksh, sh
       true                         |ksh
       type                         |ksh, sh
       typeset                      |ksh
       ulimit                       |ksh, sh
       umask                        |csh, ksh, sh
       unalias                      |csh, ksh
       unhash                       |csh
       unlimit                      |csh
       unset                        |csh, ksh, sh
       unsetenv                     |csh
       until                        |ksh, sh
       wait                         |csh, ksh, sh
       whence                       |ksh
       while                        |csh, ksh, sh

   Bourne Shell, sh,  Special Commands
       Input/output redirection is now permitted for these commands. File descriptor 1 is  the  default  output  location.  When  Job  Control  is
       enabled, additional Special Commands are added to the shell's environment.

       In addition to these built-in reserved command words, sh also uses:

       :               No effect; the command does nothing. A zero exit code is returned.

       .filename       Read  and  execute  commands from filename and return. The search path specified by PATH is used to find the directory con-
                       taining filename.

   C shell, csh
       Built-in commands are executed within the C shell. If a built-in command occurs as any component of a pipeline except the last, it is  exe-
       cuted in a subshell. In addition to these built-in reserved command words, csh also uses:

       :               Null command. This command is interpreted, but performs no action.

   Korn Shell, ksh,  Special Commands
       Input/Output  redirection  is  permitted.  Unless otherwise indicated, the output is written on file descriptor 1 and the exit status, when
       there is no syntax error, is zero.

       Commands that are preceded by one or two * (asterisks) are treated specially in the following ways:

       1.  Variable assignment lists preceding the command remain in effect when the command completes.

       2.  I/O redirections are processed after variable assignments.

       3.  Errors cause a script that contains them to abort.

       4.  Words, following a command preceded by ** that are in the format of a variable assignment, are expanded with the same rules as a  vari-
           able  assignment.  This means that tilde substitution is performed after the = sign and word splitting and file name generation are not
           performed.

       In addition to these built-in reserved command words, ksh also uses:

       * : [ arg ... ] The command only expands parameters.

       * .file [ arg ..Read the complete file then execute the commands. The commands are executed in the current shell environment.   The  search
                       path specified by PATH is used to find the directory containing file. If any arguments arg are given, they become the posi-
                       tional parameters. Otherwise, the positional parameters are unchanged. The exit status is the exit status of the last  com-
                       mand executed. the loop termination test.

       intro(1), alias(1), break(1), cd(1), chmod(1), csh(1), echo(1), exec(1), exit(1), find(1), getoptcvt(1), getopts(1), glob(1), hash(1), his-
       tory(1), jobs(1), kill(1), ksh(1), let(1), limit(1), login(1), logout(1), newgrp(1), nice(1), nohup(1), print(1),  pwd(1),  read(1),  read-
       only(1),  set(1),  sh(1),  shift(1),  suspend(1),  test(1B), time(1), times(1), trap(1), typeset(1), umask(1), wait(1), chdir(2), chmod(2),
       creat(2), umask(2), getopt(3C), profile(4), environ(5)

                                                                    29 Jun 2005                                                  shell_builtins(1)
All times are GMT -4. The time now is 02:19 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy