Return Values. – Tudor Timi Oct 16 '19 at 6:42 You want to capture what the command printed to stdout. The return value of the command is in the upper 8 bits of the return value. So you bitwise shift the return value by 8. It is used to pass the commands that can be executed in the command processor or the terminal of the operating system, and finally returns the command after it has been completed. You don't want to store the return value. This mean that something went wrong and the command was not successfully executed. The related POSIX function popen makes the output generated by command available to the caller.. An explicit flush of std::cout is also necessary … the exit code) will be 0 to indicate command success. Output: a = 10, b = 20, c = A . The void keyword, used in the previous examples, indicates that the function should not return a value. Below is the program to return multiple values using array i.e. Beware of the system return value. instead of void, and use the return keyword inside the function: Example. The system() function is a part of the C/C++ standard library. store greater value at arr[0] and smaller at arr[1]. 2. Use the exec (3) family of functions instead, but not execlp (3) or execvp (3) . The return value could be any valid expression that returns a value: a constant; a variable; a calculation, for instance (a + b) * c; call to another function that returns a value The value must be of the same (or compatible) type that the function was defined. Download Run Code. For example, setting exit 3 in the shell script, system return value is 768 (3 X 256). The return value is the exit status of the shell, see sh(1), bash(1) or whatever you have configured in SHELL environment variable. The return value (i.e. Do not use system() from a program with set-user-ID or set-group-ID privileges, because strange values for some environment variables might be used to subvert system integrity. However, C doesn't require the parentheses. [] NoteOn POSIX systems, the return value can be decomposed using WEXITSTATUS and WSTOPSIG. Implementation-defined value. If command is a null pointer, returns a nonzero value if and only if the command processor exists. By the way, the shell usually returns the last command executed exit value, but that can not be the case if you have hit the Ctrl-C key or sent a signal to the process. If a return type isn't specified, the C compiler assumes a default return type of int. The system function returns an implementation-defined value if string isn't a null pointer. (At least that's what it returns on my Solaris 7 and Red Hat 7.1) In the C Language, the required header for the system function is: #include Applies To. Many programmers use parentheses to enclose the expression argument of the return statement. Structures in C. We can also use structures in C to return more than one value from the function. For example, an int function can’t return a float value. Returning multiple values using an array (Works only when returned items are of same types): When an array is passed as an argument then its base address is passed to the function so whatever changes made to the copy of the array, it is changed in the original array. The system function returns a nonzero value if a command processor is available and string is a null pointer. We know that a structures is user defined datatype in C that can hold several data types of the same or different kind. Check in the manual page for the exit value of the shell on these cases. Required Header. Given the task is to show the working of system() in C/C++. The return value 256 actually means 1.. 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