The write system call writes data, in bytes as specified by the caller, from a buffer declared by the user in the program and then writes it into the file supplied by the calling process. In most modern operating system, a program that needs to write data to a file stored in a filesystem uses the Write system call. The file is identified by the file descriptor that is obtained from a previous call to open. Data is written to a file by calling the write function.
In C, arguments are copied by value to functions, which means that we cannot change the arguments to affect their value outside of the function. To do that, we must use pointers, which are taught later on. The function foo we defined receives one argument, which is bar. The function receives an integer, multiplies it by two, and returns the result. To execute the function foo with 1 as the argument bar , we use the following syntax:.
A function is a collection of C statements to do something specific. A C program consists of one or more functions. Every program must have a function called main. C has many built-in library functions to perform various operations, for example: sqrt function is used to find the square root of a number. Similarly, scanf and printf are also library functions, we have been using them since chapter 1 - Intro to C programming.
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