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Top Forums Shell Programming and Scripting Help with retaining variable scope Post 302555935 by bakunin on Friday 16th of September 2011 06:52:34 AM
Old 09-16-2011
Quote:
Originally Posted by justchill
Can anyone please tell me y the value is not retained.
I respectfully disagree with radoulov. The reason, why your value is not retained is because it is incremented in a subshell. This is not because of the shebang line being ignored or not, but because any command - and "sh" is a command too - is invoking its own process.

You will notice that inside your process the value is retained all right. Consider the following example script:

Code:
#!/bin/ksh

typeset -i iValue=0
typeset   chFile=""

print - "Value before: $iValue"

cat filelist | while read chFile ; do
     (( value += 1 ))
done

print - "Value after: $iValue"

exit 0

But you didn't try to retain the variable throughout a script but you inherited the variable from your commandline environment, modified it in your script and expected it to change it in the orginal commandline environment.

The problem is that when an environment inherits values it does not get the originals but copies of them - with the same names and values but still copies. If you modifiy them you are still modifying the copies, not the originals.

You can overcome this by using the ".", which tells the shell not to start a subshell but execute the script in the environment it already has:

Code:
# sh /some/script.sh
# . sh /some/script.sh

I hope this helps.

bakunin
 

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exit(1)                                                            User Commands                                                           exit(1)

NAME
exit, return, goto - shell built-in functions to enable the execution of the shell to advance beyond its sequence of steps SYNOPSIS
sh exit [n] return [n] csh exit [ ( expr )] goto label ksh *exit [n] *return [n] DESCRIPTION
sh exit will cause the calling shell or shell script to exit with the exit status specified by n. If n is omitted the exit status is that of the last command executed (an EOF will also cause the shell to exit.) return causes a function to exit with the return value specified by n. If n is omitted, the return status is that of the last command exe- cuted. csh exit will cause the calling shell or shell script to exit, either with the value of the status variable or with the value specified by the expression expr. The goto built-in uses a specified label as a search string amongst commands. The shell rewinds its input as much as possible and searches for a line of the form label: possibly preceded by space or tab characters. Execution continues after the indicated line. It is an error to jump to a label that occurs between a while or for built-in command and its corresponding end. ksh exit will cause the calling shell or shell script to exit with the exit status specified by n. The value will be the least significant 8 bits of the specified status. If n is omitted then the exit status is that of the last command executed. When exit occurs when executing a trap, the last command refers to the command that executed before the trap was invoked. An end-of-file will also cause the shell to exit except for a shell which has the ignoreeof option (See set below) turned on. return causes a shell function or '.' script to return to the invoking script with the return status specified by n. The value will be the least significant 8 bits of the specified status. If n is omitted then the return status is that of the last command executed. If return is invoked while not in a function or a '.' script, then it is the same as an exit. On this man page, ksh(1) 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. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | |Availability |SUNWcsu | +-----------------------------+-----------------------------+ SEE ALSO
break(1), csh(1), ksh(1), sh(1), attributes(5) SunOS 5.10 15 Apr 1994 exit(1)
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