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Top Forums Shell Programming and Scripting Advanced error handling in shell scripts Post 302363695 by script_man on Wednesday 21st of October 2009 05:10:53 AM
Old 10-21-2009
Advanced error handling in shell scripts

Hi all


I've got a question regarding error handling in shell scripts. My background is mainly object oriented programming languages, but for a year or so I've been doing more and more (bash) shell scripting (which I quite enjoy by the way).

To handle errors in my scripts I often find myself doing something like:

Code:
<execute some command>
  if [ $? -ne 0 ] ;then
    <handle error>
  fi

In many cases the <handle error> is the same for the commands executed, so you end up duplicating code. Thus I think it would be better to encapsulate this code in a function, e.g.

Code:
exec_cmd()
  {
    $1 # the command to be executed is passed in as an argument
    if [ $? -ne 0 ] ; then
      <handle error>
    fi
  }

And execute commands by calling this function:
Code:
exec_cmd "<some command>"

Furthermore, the function can easily be enhanced to write the command as well as the command output and return code to a log file:
Code:
exec_cmd()
{
  echo ""   >> $log_file
  echo "---------------------------------------------------------" >> $log_file
  echo "$1" >> $log_file
  $1        >> $log_file 2>&1
  return_code=$?
  if [ $return_code -ne 0 ] ; then
    echo "ERROR - $1 failed with $return_code"
    exit 1
  fi
}

exec_cmd "<cmd1>"
exec_cmd "<cmd2>"
exec_cmd "<cmd2>"
...

I found this quite handy to handle errors in my scripts. If you write command, output and return code to a log file, it also makes it quite easy to investigate problems with scripts that run in the background.


Now my question is:
How is that as a practise? Is it common? Or would it be considerd as bad and if so why? Has the bash already got something like this build in? (E.g. there might be an exit on fail option; I also know that you can start scripts with an option which outputs the commands which are being executed).

How do the experienced people here do the error handling in their scripts?

Thanks and best wishes
 

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platform::shell(n)					       Tcl Bundled Packages						platform::shell(n)

__________________________________________________________________________________________________________________________________________________

NAME
platform::shell - System identification support code and utilities SYNOPSIS
package require platform::shell ?1.1.4? platform::shell::generic shell platform::shell::identify shell platform::shell::platform shell _________________________________________________________________ DESCRIPTION
The platform::shell package provides several utility commands useful for the identification of the architecture of a specific Tcl shell. This package allows the identification of the architecture of a specific Tcl shell different from the shell running the package. The only requirement is that the other shell (identified by its path), is actually executable on the current machine. While for most platform this means that the architecture of the interrogated shell is identical to the architecture of the running shell this is not generally true. A counter example are all platforms which have 32 and 64 bit variants and where a 64bit system is able to run 32bit code. For these running and interrogated shell may have different 32/64 bit settings and thus different identifiers. For applications like a code repository it is important to identify the architecture of the shell which will actually run the installed packages, versus the architecture of the shell running the repository software. COMMANDS
platform::shell::identify shell This command does the same identification as platform::identify, for the specified Tcl shell, in contrast to the running shell. platform::shell::generic shell This command does the same identification as platform::generic, for the specified Tcl shell, in contrast to the running shell. platform::shell::platform shell This command returns the contents of tcl_platform(platform) for the specified Tcl shell. KEYWORDS
operating system, cpu architecture, platform, architecture platform::shell 1.1.4 platform::shell(n)
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