# Unix Shell Script

by Surrealist
Tags: script, shell, unix
 P: 63 I have never written a shell script, but I am trying to learn. I want to make a generic Unix shell script that will allow me to run four commands in a row... something like this... latex $filename bibtex$filename latex $filename latex$filename I would like to call the script "ltxprc.sh". How would I make this file work for any filename? For instance, if my file name were "paper", would I run a command like... sh ltxprc.sh where do I input the filename?
 Mentor P: 15,069 First, you need to modify your script so it accesses the command line arguments sent to the script: filename=\$1 You pass the filename on the command line: sh ltxprc.sh file.tex Even better is to make the shell script executable via chmod. You will need to add a "shebang" line to the very front of your script: #!/bin/sh When you do that, all you need to say is ltxprc.sh file.tex
 P: 63 Thanks for the help. That was probably the most useful response I have ever received from a message board. I gotta ask... why is it that the #!/bin/sh works? I thought that the # symbol meant "comment out" that which follows.
Mentor
P: 15,069
Unix Shell Script

 Quote by Surrealist I gotta ask... why is it that the #!/bin/sh works? I thought that the # symbol meant "comment out" that which follows.
The # symbol is indeed a comment to the shell. The shell, however, is not what runs runs programs (directly, that is). The exec family of functions are what run programs on a Unix machine. The first thing exec does when asked to run a program is read the first two bytes of the program. When those first two bytes are "#!", exec does something quite special: It uses the line to indicate what program should be executed to run the script file. For example, you used #!/bin/sh . The #! tells exec this is an executable script. The exec invokes /bin/sh to run the script. Now /bin/sh reads lines from the script. Now we get back to your question: the first line is just a comment; /bin/sh does nothing with it.