Introduction to Scripting - 2

The objective of this lab is to introduce scripting with some sample scripts.

1. Download the sample scripts from ops105 account on matrix. Replace MYSENECA-USER with your MySeneca username in the example below

   scp -r MYSENECA-USER@matrix.senecacollege.ca:~mark.fernandes/ops105/scripts/all-scripting-examples  /tmp/scripting
   

2. List the contents of the scripts you just downloaded

   cd /tmp/scripting
   ls -F
   

   00-hello*
   01-ask_and_hello*
   02-if_else*
   03-if_else-is_directory*
   04-if_else-needs_3_arguments*
   a*
   misc/
   scripting_symbols.txt
   

3. The scripts we are interested in are 00-hello, 01-ask_and_hello, 02-if_else, and a few more. View the contents of file 00-hello are:

   cat 00-hello
   

   #!/bin/bash
   #
   # OPS145:       script 1 - introduction (output only)
   # Script name:  hello
   # Purpose:      display a message
   
   
   # display message to user
   echo "Hello bash"
   

   Run the 00hello script.

   ./00-hello
   

   Hello bash
   

4. Next look at the contents of 01-ask_and_hello example.

   cat 01-ask_and_hello
   

   #!/bin/bash
   
   # ask user for their name
   read -p "What is your name? " NAME
   
   # show custom message to user
   echo "Hello $NAME from OPS105 scripting"
   
   

   Run the 01-ask_and_hello script.

   ./01ask_and_hello
   

   What is your name? mark
   Hello mark from OPS105 scripting
   

1. 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
   

2. 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
   

3. 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