- What is the $? (dollar question mark) variable in shell scripting?
The shell treats several parameters specially These parameters may only be referenced; assignment to them is not allowed [ ]? Expands to the exit status of the most recently executed foreground pipeline ANSI C and POSIX then recommend that: 0 means the program was successful other values: the program failed somehow
- linux - What does $@ mean in a shell script? - Stack Overflow
The shell splits tokens based on the contents of the IFS environment variable Its default value is \t\n; i e , whitespace, tab, and newline Expanding "$@" gives you a pristine copy of the arguments passed Expanding $@ may not
- Difference between $ {} and $ () in a shell script - Super User
The above (along with many more forms of ${parameter…something_else} constructs) are discussed at greater length in the shell’s man page, bash(1) A Note on Quotes Note that you should always quote shell variables unless you have a good reason not to, and you’re sure you know what you’re doing By contrast, while braces can be
- regex - Meaning of =~ operator in shell script - Stack Overflow
The return value is 0 if the string matches the pattern, and 1 otherwise If the regular expression is syntactically incorrect, the conditional expression's return value is 2 If the shell option nocasematch is enabled, the match is performed without regard to the case of alphabetic characters
- What does $# mean in shell? - Unix Linux Stack Exchange
You can always check the man page of your shell man bash says: Special Parameters # Expands to the number of positional parameters in decimal Therefore a shell script can check how many parameters are given with code like this: if [ "$#" -eq 0 ]; then echo "you did not pass any parameter" fi
- bash - Shell equality operators (=, ==, -eq) - Stack Overflow
What is the difference between =, == and -eq in shell scripting? Is there any difference between the following?
- shell - Difference between sh and Bash - Stack Overflow
Shell - "Shell" is a program, which facilitates the interaction between the user and the operating system (kernel) There are many shell implementations available, like sh, Bash, C shell, Z shell, etc Using any of the shell programs, we will be able to execute commands that are supported by that shell program Bash - It derived from Bourne
- What are the special dollar sign shell variables? - Stack Overflow
$0 is the name of the shell or shell script Most of the above can be found under Special Parameters in the Bash Reference Manual Here are all the environment variables set by the shell For a comprehensive index, please see the Reference Manual Variable Index
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