Linux learning-command line parameters, functions

Shell

Command line parameters

• Command line parameters can be read using $ 1 $ 2 ... $ {10} .. $ n
• $ 0 represents the script name
• $ * And $ @ represent all positional parameters
• $ # Represents the number of positional parameters

function

• function fname () {
  Command
  }

• Function execution:

  • fname
  • Cancel a function: unset fname

Variable of function scope

• local variable names only work inside functions

Function parameters

• $1 $2 $3...$n

System function library

• /etc/init.d/functions Function library built by the system
• / etc / profile stores system environment variables
• Both .bashrc and .bash_profile have functions that determine the execution order of the program. Both files are under the home directory of the root directory

Self-built function library

• Use the source function script file to "import" the function
  • source /etc/init.d/functions

Scripting to capture signals

• kill sends signal 15 to the application by default
• Ctrl + c Send No. 2 signal to the application
• No. 9 signal cannot be blocked
• Example:
  • trap "echo sig 15" 15 capture the 15th signal, output sig 15 if it is captured