Shell scripts

• The special shell characters used to separate words are termed internal field separators and are defined by the shell variable IFS
• Several commands on the same line must be separated by a semicolon
• A script can use pipes and redirection both internally and externally, that is pipes and redirection can be part of the commands within a script and the script as a whole can use pipes and redirection to control input and output
• Interactive scripts are based on UNIX shell commands read and echo
• The read command can be followed by a list of variable names. If the response consists of several words, the first variable gets the first word, the second variable the second word and so on. If there are more words than variables, all left-over words get assigned to the last variable. If there are more variables than words, the unused variables are not assigned values.
• Example:
  read name
  echo Hello $name

• Shell script arguments: positional parameters
• Looping and Making Choices
  • The for Loop
  • The while And until Loops
  • The if then else Structure
  • The case Statement
  • The test command