Linux Shell functions

Introduction

Body

$?

$? is a shell variable that represents the exit state of the last execution command. 0 for success, not 0 for failure. Remember: $? Always indicates the exit state of the shell command after the last execution, and when the function is finished, if another command is executed, then $? no longer represents the state after the function is executed. and indicates the exit status of the other command.

$$ The shell itself PID (ProcessID) $!pid $ for Shell last run background process?end code of the last Run command (return value) $-flag with SET command list $*all parameter lists. As"$*":in"$1$2... $n"all parameters in the form of output. [email protected] all parameter lists. As"[email protected]":in the form of multiple lines"$1" "$2"... .."$n"output all parameters. $# Number of arguments added to the shell0the name of the shell itself $1~ $n Each parameter value added to the shell. $ $ is the 1th parameter, and the $ = is the 2nd parameter .... 

Cases:

Vim a.sh

 #!/bin/bash  printf "The complete list is%s\n" "$$"  printf "The complete list is%s\n" "$!"  printf "The complete list is%s\n" "$?"  printf "The complete list is%s\n" "$*"  printf "The complete list is%s\n" "[email protected]"  printf "The complete list is%s\n" "$#"  printf "The complete list is%s\n" " $"  printf "The complete list is%s\n" " $"  printf "The complete list is%s\n" " $"

Summary

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Linux Shell functions