安裝中文字典英文字典辭典工具!
安裝中文字典英文字典辭典工具!
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- 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
- 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
- bash - Shell equality operators (=, ==, -eq) - Stack Overflow
What is the difference between =, == and -eq in shell scripting? Is there any difference between the following?
- 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
- 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
- Meaning of $? (dollar question mark) in shell scripts
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
- shell - What does -- (double dash double hyphen) mean? - Unix . . .
In man bash we can read in Shell Builtin Commands section : Unless otherwise noted, each builtin command documented in this section as accepting options preceded by -accepts --to signify the end of the options The :, true, false, and test builtins do not accept options and do not treat --specially
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