4.9 Shell Script #2
Shell Scripts are like DOS batch files. All systems have a way of
automating the command line interface. Some work better than others.
UNIX/Linux systems provide multiple ways of automating the command line
interface. The programs that do this are called shells. On this system
the following are listed in the file /etc/shells.
# /etc/shells: valid login shells
/bin/ash
/bin/bash
/bin/csh
/bin/sh
/usr/bin/es
/usr/bin/ksh
/usr/bin/rc
/usr/bin/tcsh
/usr/bin/zsh
There are other shells and other ways of automating program execution on
UNIX/Linux systems. The programming language Perl is a good example.
- Create a shell script with the editor to compile
and run the PASCAL program from your previous labs
Lab 4.5: "Enter a PASCAL program" and
Lab 4.6: "Pascal program compile and run".
UNIX/Linux shell scripts use a
# at the beginning of the line to
indicate a comment. The first two characters in the file are special.
If the characters are #!, then the line indicates which program
will be used to run the script.
Use the file name: pascal.
#!/bin/bash
# pascal - your name - today's date
#
gpc -o trip trip.pas
trip << endofdata
2100
70
40
1.69
endofdata
A few notes explaining the shell script. First, the script is going to
use the bash shell. And its executable is located in the
file !/bin/bash. gpc is the Pascal compiler. The
output
of the compiler is directed to the file trip. The line
"trip << endofdata" will run the program using input from the
shell script down to the line containing "endofdata".
The four lines of data will go into the program as miles, speed, miles per
gallon, and price per gallon just as if they were entered from the
keyboard. The output will still go to the screen.
- Next change the permissions on the file pascal so that you
can execute it.
chmod a+x pascal
-
Then execute the shell script.
pascal
It should display on your terminal the results of the trip calculations.
When you have this working, re-run the program sending the output to the
printer.
pascal | lpr
Turn in the printout from section 4.9 marked with:
Your-Name
Lab 4.9: Shell Script #2
TABER CIS135
Instructor: ltaber@pima.edu ** My new Home at GeoApps in Tucson ** The Pima College Site ** The Mad Dr. G.'s home page on phred.
