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System Calls

System calls are invoked ...
  • directly, through a library of system calls
    • documented in Unix Programmers Manual section 2
      (e.g. man 2 open)
  • indirectly, through functions in the C libraries
    • documented in Unix Programmers Manual section 3
      (e.g. man 3 fopen)
Example of system call library vs C library
  • file descriptors, open(), close(), read(), write()
    (via #include <unistd.h>)
  • file pointers (FILE*), fopen(), fclose(), fgets(), scanf(),printf()
    (via #include <stdio.h>)