Introduction to Scripting

The objective of this lab is to introduce scripting

1. A simple script, but first run the following command

   echo "OPS105: Hello Bash"
   

   OPS105: Hello Bash
   

2. Make a file, using your favourite editor, called hello and put the following information in it:

   #!/bin/bash
   
   echo "OPS105: Hello Bash"
   

3. So the contents of file hello are:

   cat hello
   

   #!/bin/bash
   
   echo "OPS105: Hello Bash"
   

4. The properties of a file and a script are slightly different, but it is significant. Let us check the initial properties of hello before we make it a script, and we check whether or not we can run the file simply by using its name

   ls -l hello
   hello
   

   -rw-r--r-- 1 mfernand_stu mfernand_stu 39 Nov 12 16:27 hello
   -bash: ./hello: Permission denied
   

5. Change the permissions of hello to make it a script, and attempt to run it again. Observe the result.

   chmod a+x hello
   ls -l hello
   hello
   

   -rwxr-xr-x 1 mfernand_stu mfernand_stu 39 Nov 12 16:27 hello
   OPS105: Hello Bash
   

6. Now make a directory called rough_work and put hello in it, then attempt to run it. Notice the error message. Why?

   mkdir -p rough-work
   mv hello rough-work
   hello
   

   -bash: ./hello: command not found
   

7. That error happened because the script hello was no longer in the search path ($PATH). To run it properly we can do either one of the following:

   • call it with the correct path to hello

   rough-work/hello
   

   OPS105: Hello Bash
   

   • change your pwd to the location where the hello script lies and call it from there

   pwd
   cd rough-work
   pwd
   hello
   

   /tmp
   /tmp/rough-work
   OPS105: Hello Bash