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- bash - What are the special dollar sign shell variables . . . - Stack . . .
In Bash, there appear to be several variables which hold special, consistently-meaning values For instance, myprogram amp;; echo $! will return the PID of the process which backgrounded myprog
- bash - What is the purpose of in a shell command? - Stack Overflow
$ command one command two the intent is to execute the command that follows the only if the first command is successful This is idiomatic of Posix shells, and not only found in Bash It intends to prevent the running of the second process if the first fails You may notice I've used the word "intent" - that's for good reason
- bash - Shell equality operators (=, ==, -eq) - Stack Overflow
If not quoted, it is a pattern match! (From the Bash man page: "Any part of the pattern may be quoted to force it to be matched as a string ") Here in Bash, the two statements yielding "yes" are pattern matching, other three are string equality:
- shell - Bash regex =~ operator - Stack Overflow
The =~ operator is a regular expression match operator This operator is inspired by Perl's use of the same operator for regular expression matching The [[ ]] is treated specially by bash; consider that an augmented version of [ ] construct: [ ] is actually a shell built-in command, which, can actually be implemented as an external command Look at your usr bin, there is most likely a
- What does $# mean in bash? - Ask Ubuntu
Furthermore, when you use bash -c, behavior is different than if you run an executable shell script, because in the latter case the argument with index 0 is the shell command used to invoke it
- bash - What does lt; lt; lt; mean? - Unix Linux Stack Exchange
Take a look at the Bash man page This notation is part of what's called a here documents here strings It allows you the ability to generate multi-line data input as one continuous string The variation you're asking about is called a here string excerpt from Bash man page Here Strings A variant of here documents, the format is: <<<word The word is expanded and supplied to the command on
- linux - What does $@ mean in a shell script? - Stack Overflow
What does a dollar sign followed by an at-sign (@) mean in a shell script? For example: umbrella_corp_options $@
- Meaning of $? (dollar question mark) in shell scripts
What does echo $? mean in shell programming?true echo $? # echoes 0 false echo $? # echoes 1 From the manual: (acessible by calling man bash in your shell) ? Expands to the exit status of the most recently executed foreground pipeline By convention an exit status of 0 means success, and non-zero return status means failure Learn more about exit statuses on wikipedia There are other special
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