01-31-2012
System calls in UNIX
Hi i am very new to programming in UNIX and don't understand the difference between a system call and a normal function call. Also can I implement system calls from within a program? If so could someone please give me an example of a system call from within a program. Lastly, when creating a program related to systems programming is it necessary to be in a specific shell? Sorry if these questions are pretty basic but I am completely lost here. Any help would be greatly appreciated.
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LEARN ABOUT FREEBSD
getpid
GETPID(2) BSD System Calls Manual GETPID(2)
NAME
getpid, getppid -- get parent or calling process identification
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <sys/types.h>
#include <unistd.h>
pid_t
getpid(void);
pid_t
getppid(void);
DESCRIPTION
The getpid() system call returns the process ID of the calling process. Though the ID is guaranteed to be unique, it should NOT be used for
constructing temporary file names, for security reasons; see mkstemp(3) instead.
The getppid() system call returns the process ID of the parent of the calling process.
ERRORS
The getpid() and getppid() system calls are always successful, and no return value is reserved to indicate an error.
SEE ALSO
fork(2), getpgrp(2), kill(2), setpgid(2), setsid(2), exec(3)
STANDARDS
The getpid() and getppid() system calls are expected to conform to ISO/IEC 9945-1:1990 (``POSIX.1'').
HISTORY
The getpid() function appeared in Version 7 AT&T UNIX.
BSD
November 2, 2006 BSD