CSC209H5 Chapter Notes - Chapter 6: Gnu Compiler Collection, Child Process, C Data Types
22 Mar 2018
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Csc209h5s - software programming and tools (winter 2018) #define max_line_length 80 int main ( int argc, char *argv[] ) { File *fp; char s [max_line_length + 1 ]; fp = fopen(argv[ 1 ], "r" ); fgets( s , max_line_length, fp); printf ( "one line from the file: %s, s); return 0; In this program, we use fopen to open the file that is given as a command line argument. Each system call returns a special value to indicate an error. System calls that return a pointer will return null if there is an error. System calls that return an integer will return -1 if there is an error. The return value itself cannot be solely used to indicate the error type. Errno has a return type of return int. When an error occurs in the system call, the system calls return. 1 or null depending on the return and sets a value for errno.
