C quick reference

Common library functions on one page.

Function	Purpose
`printf / scanf`	Formatted output and input
`fgets(buf, n, stdin)`	Read a line safely
`strlen(s)`	String length
`strcpy / strncpy`	Copy a string
`strcmp(a, b)`	Compare strings; 0 means equal
`malloc / free`	Get and release heap memory
`fopen / fclose`	Open and close a file
`abs / rand`	Absolute value / random number