Lab 4 Advanced Scripting and Regular Expressions

Procedure

1. Using nano, the script fib was written to print the n^th Fibonacci number. It is interesting to note that a function defintion in Bash is similar to C, obviously excluding the return type. This is despite the fact that Bash interprets commands while C compiles to assembly language.
2. pgrep -u $(whoami) was used to identify the processes owned by the current user. This output could be piped into wc -l to determine the number of lines, and therefore the number of processes, owned. The final command was pgrep -u $(whoami) | wc -l.
3. The command ls -l | grep '-......r' printed all files in world-readable files in the current directory by checking whether the seventh character of the permissions string is 'r'.

Commands

• wc is used to count the number of words in piped input. The -l flag can be used to count the number of lines.
• finger retrieves information about the users logged in.
• whoami returns the current user's username.
• head returns the first 10 lines of any piped input by default. The -n flag can be used to change the number of lines output.
• tail returns the last 10 lines of any pipied input by default, although this can also be adjusted using the -n flag.
• grep prints lines that contain a match for one or more patterns, and the -E flag allows the use of extended regular expressions.
• sed allows regex transformations on an input stream, and the -E flag allows the use of extended regular expressions.