Executing multiple commands

• command1; command2; command3
  • Each command will be executed one after the other
• command1 && command2 && command3
  • This works as a logical AND
  • The subsequent commands after command-n will not run if the previous command resulted in an error
• command1 || command2 || command3
  • This works as a logical OR
  • The subsequent commands after command-n will not run if the previous command resulted in a success

(<command>)

• We can run any command enclosed within parentheses to execute them in a subshell, and return back the result

  

  • All three commands are executed in a subshell, subshell returns result to the shell

• We can execute a subshell within a subshell too

• $BASH_SUBSHELL contains the level of subshell where a particular command is running

  

File descriptors

Every command in Linux has 3 file descriptors

• stdin $(0)$
  • It is a pointer to a stream that is coming from the keyboard (or the user input)
• stdout $(1)$
  • Points to the screen where the output is made