What does mean in a shell script

Question

What does a dollar sign followed by an at-sign     mean in a shell script   For example   umbrella corp options

User · Accepted Answer

is all of the parameters passed to the script    For instance  if you call   someScript sh foo bar then    will be equal to foo bar   If you do     someScript sh foo bar   and then inside someScript sh reference   umbrella corp options        this will be passed to umbrella corp options with each individual parameter enclosed in double quotes  allowing to take parameters with blank space from the caller and pass them on

User · Answer

is nearly the same as     both meaning  all command line arguments    They are often used to simply pass all arguments to another program  thus forming a wrapper around that other program    The difference between the two syntaxes shows up when you have an argument with spaces in it  e g   and put    in double quotes   wrappedProgram            this is correct and will hand over all arguments in the way       we received them  i  e  as several arguments  each of them       containing all the spaces and other uglinesses they have  wrappedProgram            this will hand over exactly one argument  containing all       original arguments  separated by single spaces  wrappedProgram          this will join all arguments by single spaces as well and       will then split the string as the shell does on the command       line  thus it will split an argument containing spaces into       several arguments    Example  Calling  wrapper  one two    three  four five  six seven    will result in         wrappedProgram  one two    three  four five  six seven        wrappedProgram  one two    three four five six seven                                    These spaces are part of the first                                   argument and are not changed        wrappedProgram one two three four five six seven

User · Answer

Meaning   In brief     expands to the positional arguments passed from the caller to either a function or a script  Its meaning is context-dependent  Inside a function  it expands to the arguments passed to such function  If used in a script  not inside the scope a function   it expands to the arguments passed to such script     cat my-sh     bin sh echo           my-sh  Hi   Hi      put      echo          put  Hi   Hi      Word splitting   Now  another topic that is of paramount importance when understanding how    behaves in the shell is word splitting  The shell splits tokens based on the contents of the IFS variable  Its default value is  t n  i e   whitespace  tab  and newline   Expanding      gives you a pristine copy of the arguments passed  However  expanding    will not always  More specifically  if the arguments contain characters from IFS  they will split     Most of the time what you will want to use is       not

User · Answer

These are the command line arguments where        stores all the arguments in a list of string      stores all the arguments as a single string      stores the number of arguments

User · Answer

From the manual     Expands to the positional parameters  starting from one  When the expansion occurs within double quotes  each parameter expands to a separate word  That is   quot    quot  is equivalent to  quot  1 quot   quot  2 quot       If the double-quoted expansion occurs within a word  the expansion of the first parameter is joined with the beginning part of the original word  and the expansion of the last parameter is joined with the last part of the original word  When there are no positional parameters   quot    quot  and    expand to nothing  i e   they are removed

User · Answer

The usage of a pure    means in most cases  hurt the programmer as hard as you can   because in most cases it leads to problems with word separation and with spaces and other characters in arguments   In  guessed  99  of all cases  it is required to enclose it in         is what can be used to reliably iterate over the arguments   for a in       do something with   a   done

[linux] What does $@ mean in a shell script?

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