Meeting Minutes - sh - Posix Shell Session - Day 4 - July 09, 2020

Here are the topics we covered on day four,

  • importance of exitcode (or returncode)
  • howto retrive last executed command’s exitcode through ${?} special variable
  • howto use this exitcode in if-elif-else-fi command
  • howto use case-esac command
  • introducing ‘for-do-done’ loop
  • how this is different from regular for loop in ‘C’ programming
  • iterating through static values using for loop
  • introducing command substitution through $()
  • how command substitution can generate dynamic values for each iteration in for loop
  • importance of command substitution
  • introducing ‘while-do-done’ loop
  • introducing variable expansion, what exactly means ‘$’ before a word
  • difference between ${var} and “${var}”
  • different way to expand variables using :+, :=, :? and :-
  • howto do arithmetic expansion using $(())
  • built-in special variables which ‘sh’ provides by default
  • meaning of ‘${$}’
  • meaning of ‘${?}’
  • meaning of ‘${!}’
  • running background jobs using ‘&’ seperator
  • introducing ‘jobs’ command, also ‘bg’ and ‘fg’ commands

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