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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">The ${0} refers to the current program name.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">It is not assigning X to anything – it is assigning the value of X. If the condition is true the it is setting X to the present working directory followed
by the program name. If not true it is setting it to just the program name.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">So if your program were called billybob.sh and it were in /home/bobbiesue then $0 = billybob.sh (as does ${0}) and ${PWD}/${0} = /home/bobbiesue/billybob.sh.
If the condition is true then X gets set to billybob.sh and if not true X gets set to /home/bobbiesue/billybob.sh.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">After that it is trying to cd to the directory that ccontains $0 which would be “.” (current directory) if true or /home/bobbiesue if false.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I don’t know if the #/ is trying to do in the conditional though. Out of context with the rest of the script it doesn’t mean anything to me. Testing it
as is I found ${0#/} does equal ${0}.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">ksh is available for Linux so you could try to add it and run this in ksh. You could then insert echo statements just before the conditional:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">echo ${0#/}<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">echo ${0}<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Note that ${0} might NOT be the actual program if this is calling a function within the program.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Does the interpreter line at top of script specify ksh or bash or sh? If sh what is that linked to?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> ale-bounces@ale.org [mailto:ale-bounces@ale.org]
<b>On Behalf Of </b>Jonathan Meek<br>
<b>Sent:</b> Tuesday, March 11, 2014 1:44 PM<br>
<b>To:</b> Atlanta Linux Enthusiasts<br>
<b>Subject:</b> [ale] Stupid Question on ksh script<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Hello everyone, <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I am reviewing a script at work in order to understand that someone has done before me. They decided to ksh to write their scripting. There's an if statement I don't quite get and would be grateful for some light on the issue. Here's the
code snippet: <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New"">if [ ${0#/} = ${0} ] ; then</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> X=${PWD}/${0}</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> else</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> X=${0}</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> fi</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Courier New""> cd $(dirname ${X})</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-family:"Arial","sans-serif"">Based on my own searching for meaning and understanding and somewhat limited look into the man pages for ksh(couldn't remember how to search within vi), here's what I think is going on:</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Arial","sans-serif"">The if statement is checking what shell is currently running and as long as it is the expected shell, it will assign X to ${PWD}/${0}. If not, it will assign X to ${0}. Then it will change
directories based on the output of dirname, which could be the current directory or the directory that variable X is at. </span><o:p></o:p></p>
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</blockquote>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-family:"Arial","sans-serif"">Does this sound right or I am missing something? </span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-family:"Arial","sans-serif"">Regards, </span><o:p></o:p></p>
</div>
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<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal"><span style="font-family:"Arial","sans-serif"">Jonathan</span><o:p></o:p></p>
</div>
</div>
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