fk1.c // c program main()
{ int PID, pid; pid = getpid(); printf("\n The current process ID is %d\n", pid); PID = fork(); if (PID==0) { printf("\n The child process prints this message from here...... \n"); printf("\nPID value in the child process = %d\n", PID); pid = getpid(); printf("\n The child process id is %d\n", pid); printf("\n The child process now terminates"); } else { printf("\n The parent process prints out this message from here...... \n"); printf("\nPID value in the parent process = %d\n", PID); pid = getpid(); printf("\n The parent process id is %d\n", pid); printf("\n The parent process now terminates"); } } fk2.c //c program
#include
pid = getpid(); printf("\n The current process ID is %d\n", pid); PID = fork(); if (PID==0) { printf("\n The child process prints this message from here...... \n"); printf("Enter a value:\n"); scanf("%s", buf); printf("The child got the input buf...%s\n ", buf); printf("\nPID value in the child process = %d\n", PID); pid = getpid(); printf("\n The child process id is %d\n", pid); printf("\n The child process now terminates"); } else { printf("\n The parent process prints out this message from here...... \n"); /* scanf("%s", buf); printf("The parent got the input buf...%s\n", buf); */ printf("\nPID value in the parent process = %d\n", PID); pid = getpid(); printf("\n The parent process id is %d\n", pid); printf("\n The parent process now terminates"); } }
fk3.c // c program
#include
pid = getpid(); printf("\n The current process ID is %d\n", pid); PID = fork(); if (PID==0) { printf("\n The child process prints this message from here...... \n"); printf("Enter a value:\n"); scanf("%s", buf); printf("The child got the input buf...%s\n ", buf); printf("\nPID value in the child process = %d\n", PID); pid = getpid(); printf("\n The child process id is %d\n", pid); printf("\n The child process now terminates"); } else { printf("\n The parent process prints out this message from here...... \n"); pid = wait(&status); printf("\n The parent process waits until the child process terminates...", pid); printf("\nPID value in the parent process = %d\n", PID); pid = getpid(); printf("\n The parent process id is %d\n", pid); printf("\n The parent process now terminates"); } }
fk4.c //c program
#include
pid = getpid(); printf("\n The current process ID is %d\n", pid); PID = fork(); if (PID==0) { printf("\n The child process prints this message from here...... \n"); printf("Enter a value:\n"); scanf("%s", buf); printf("The child got the input buf...%s\n ", buf); printf("\nPID value in the child process = %d\n", PID); pid = getpid(); printf("\n The child process id is %d\n", pid); printf("\n The child process now terminates"); } else { printf("\n The parent process prints out this message from here...... \n"); scanf("%s", buf); printf("The parent got the input buf...%s\n", buf); printf("\nPID value in the parent process = %d\n", PID); pid = getpid(); printf("\n The parent process id is %d\n", pid); printf("\n The parent process now terminates"); } }
pro3-10.c
#include
/* fork a child process */ pid = fork();
if (pid < 0) {/* error occurred */ fprintf(stderr, "Fork failed"); exit(-1); } else if (pid == 0) {/* code section for child process */ execlp("/bin/ls", "ls", NULL); } else {/* parent code section */ /* parent will wait until the child to complete */ wait(NULL); printf("child complete "); exit(0); } }// of main
Win32App.c
#include "stdafx.h" #include
ZeroMemory( &si, sizeof(si) ); si.cb = sizeof(si); ZeroMemory( &pi, sizeof(pi) );
// Start the child process. if( !CreateProcess( NULL, // No module name (use command line). "C:\\WINDOWS\\system32\\mspaint.exe", // Command line. NULL, // Process handle not inheritable. NULL, // Thread handle not inheritable. FALSE, // Set handle inheritance to FALSE. 0, // No creation flags. NULL, // Use parent's environment block. NULL, // Use parent's starting directory. &si, // Pointer to STARTUPINFO structure. &pi ) // Pointer to PROCESS_INFORMATION structure. ) { printf( "CreateProcess failed (%d).\n", GetLastError() ); return -1; }
// Wait until child process exits. WaitForSingleObject( pi.hProcess, INFINITE );
// Close process and thread handles. CloseHandle( pi.hProcess ); CloseHandle( pi.hThread ); return 0; } shm-posix.c #include
/** allocate a shared memory segment */ segment_id = shmget(IPC_PRIVATE, segment_size, S_IRUSR | S_IWUSR);
/** attach the shared memory segment */ shared_memory = (char *) shmat(segment_id, NULL, 0); printf("shared memory segment %d attached at address %p\n", segment_id, shared_memory);
/** write a message to the shared memory segment */ sprintf(shared_memory, "Hi there!");
/** now print out the string from shared memory */ printf("*%s*\n", shared_memory); /** now detach the shared memory segment */ if ( shmdt(shared_memory) == -1) { fprintf(stderr, "Unable to detach\n"); }
/** now remove the shared memory segment */ shmctl(segment_id, IPC_RMID, NULL);
return 0; }
do_functions.c
#include
for (i=0; i<4; i++) { printf("doing one thing\n"); for (j=0; j <10000; j++) { (*pnum_times)++; x = x + 1; }
} } void do_another_thing(int *pnum_times) { int i, j, x;
for (i=0; i<4; i++) { printf("doing another thing\n"); for (j=0; j <10000; j++) { (*pnum_times)++; x = x + 1; } } } void do_wrap_up(int one_times, int another_times) { int total;
total = one_times + another_times; printf("wrap up: one thing %d, another %d, total %d\n", one_times, another_times, total); }
simple.c
#include
con_simple.c
#include
#include
main() { pid_t child1_pid, child2_pid; int status;
/* initialize shared memory segment */
if(( shared_mem_id = shmget(IPC_PRIVATE, 2*sizeof(int), IPC_CREAT|0666)) <0) perror("shmget failed"); /* if (( shared_mem_ptr = (int *)shmat(shared_mem_id, (void *)0, 0)) == (int *) -1) perror("shmat failed"); */
if (( shared_mem_ptr = (int *)shmat(shared_mem_id, NULL, 0)) == (int *) -1) perror("shmat failed");
r1p = shared_mem_ptr; r2p = shared_mem_ptr + 1;
*r1p = (int) 0; *r2p = (int) 0;
if ((child1_pid = fork()) == 0) { /* first child does this.... */ do_one_thing(r1p); exit(status); } /* Now parent does this checkings.... */ if ((child2_pid = fork()) == 0) { /* second child does this.... */ do_another_thing(r2p); exit(status); }
/* Parent */ waitpid(child1_pid, &status, 0);
if(WIFEXITED(status)) printf("Child exited with code %d\n", WEXITSTATUS(status)); else printf("Child terminated abnormally\n");
waitpid(child2_pid, (int *) status, 0); do_wrap_up(*r1p, *r2p); }
simple_thread.c
#include
void do_one_thing(int *); void do_another_thing(int *); void do_wrap_up(int, int); int r1 = 0, r2 = 0;
main() {
pthread_t thread1, thread2;
pthread_create(&thread1, NULL, (void *) do_one_thing, (void *) &r1); pthread_create(&thread2, NULL, (void *) do_another_thing, (void *) &r2);
pthread_join(thread1, NULL); pthread_join(thread2, NULL);
do_wrap_up(r1, r2);
} makefile
CC = gcc CFLAGS = -g THREAD_CFLAGS = ${CFLAGS} -pthread
all : simple con_simple simple_thread do_functions.o : do_functions.c $(CC) $(CFLAGS) -c do_functions.c simple : simple.o do_functions.o $(CC) $(CFLAGS) do_functions.o simple.o -o simple con_simple : con_simple.o do_functions.o $(CC) $(CFLAGS) do_functions.o con_simple.o -o con_simple simple_thread : simple_thread.o do_functions.o $(CC) $(THREAD_CFLAGS) do_functions.o simple_thread.o -o simple_thread clean : rm -f *.o *~ *# core a.out\ simple con_simple simple_thread
Another thread example sumThread.c
/** * A pthread program illustrating how to * create a simple thread and some of the pthread API * This program implements the summation function where * the summation operation is run as a separate thread. * * Most Unix/Linux/OS X users * gcc thrd.c -lpthread * * Solaris users must enter * gcc thrd.c -lpthreads * */
#include
/* get the default attributes */ pthread_attr_init(&attr);
/* create the thread */ pthread_create(&tid,&attr,runner,argv[1]);
/* now wait for the thread to exit */ pthread_join(tid,NULL); printf("sum = %d\n",sum); }
/** * The thread will begin control in this function */ void *runner(void *param) { int i, upper = atoi(param); sum = 0;
if (upper > 0) { for (i = 1; i <= upper; i++) sum += i; }
pthread_exit(0); }
mserver.c
#include
#define MSGKEY 75 #define ACK "msgserv received the following message: " struct msgform { long mtype; char mtext[2048]; } sndbuf, rcvbuf, *msgp; int msgid; main() { extern int errno; int i, rtrn; msgid = msgget(MSGKEY, 0777|IPC_CREAT);
for(;;) { msgp = &rcvbuf; msgrcv(msgid, msgp, 2048, 1, 0); printf("\n%s\n", rcvbuf.mtext);
msgp = &sndbuf; strcpy(sndbuf.mtext, ACK); strcat(sndbuf.mtext, rcvbuf.mtext); msgp->mtype = 10; rtrn=msgsnd(msgid, msgp, sizeof(sndbuf.mtext), 0); if (rtrn == -1) { printf("\n msgsnd() system call failed, Error # = %d\n", errno); exit(0); } } }
mclient.c
#include
#define MSGKEY 75
struct msgform { long mtype; char mtext[2048]; } sndbuf, rcvbuf, *msgp; main() { extern int errno; int i, c, msgid; int rtrn, msgsz;
msgid = msgget(MSGKEY, 0777); msgp = &sndbuf; msgp->mtype = 1; printf("\n Enter your message to be delivered to the server:\n"); for (i = 0; ((c=getchar())!=EOF); i++) sndbuf.mtext[i] = c; msgsz = i + 1;
rtrn = msgsnd(msgid, msgp, msgsz, 0); if (rtrn == -1) { printf("\n msgsnd() system call failed, error # = %d\n", errno); exit(0); }
msgp = &rcvbuf; msgrcv(msgid, msgp, 2048, 10, 0); printf("\n%s\n", rcvbuf.mtext); } DateClient.java import java.net.*; import java.io.*; public class DateClient { public static void main(String[] args) { try { // this could be changed to an IP name or address other than the localhost Socket sock = new Socket("127.0.0.1",6013); InputStream in = sock.getInputStream(); BufferedReader bin = new BufferedReader(new InputStreamReader(in));
String line; while( (line = bin.readLine()) != null) System.out.println(line);
sock.close(); } catch (IOException ioe) { System.err.println(ioe); } } }
DateServer.java import java.net.*; import java.io.*; public class DateServer { public static void main(String[] args) { try { ServerSocket sock = new ServerSocket(6013);
// now listen for connections while (true) { Socket client = sock.accept(); // we have a connection
PrintWriter pout = new PrintWriter(client.getOutputStream(), true); // write the Date to the socket pout.println(new java.util.Date().toString());
// close the socket and resume listening for more connections client.close(); } } catch (IOException ioe) { System.err.println(ioe); } } }
Implementing a simple shell by exec()
#include
for(;;) { printf("mysh ready$$"); /* prompting mysh reddy $$ */ gets(cmd); /* read a command */ if (strcmp(cmd, "exit") == 0) return(0); background(cmd); /* start a background job */ }
} void background(char *cmd) { char *argv[MAXARG]; int pid, i = 0; /* to fill in argv */ argv[i++] = strtok(cmd, WHITE); while (i < MAXARG && (argv[i++] = strtok(NULL, WHITE)) != NULL); if ( (pid = fork()) == 0) /* The child process executes background job */ { execv(argv[0], argv); // execl("/bin/ls", "ls", "-a", "-l", 0); exit(1); /* execv failed */ } else if (pid < 0) {
fprintf(stderr, "fork failed \n"); perror("background"); }
}
pexec.c
#include
//Not useful char *const ps_envp[] = {"PATH=/bin/ls:/usr/bin", "TERM=console", 0}; int main() { printf("Replace this process with new program image by exec family \n");
// execl("/bin/ps", "ps", "-ax", 0); //assume ps is in bin directory // execlp("ps", "ps", "-ax", 0); //assume /bin is in PATH execle("/bin/ls", "-Fs", 0, ps_envp); //passes own environment
// execv("/bin/ps", ps_argv); // execvp("ps", ps_argv); // execve("/bin/ps", ps_argv, ps_envp);
printf("Done.\n"); exit(0); }
ptrace.c
#include
server2.c //UNIX INET domain socket server
/* Make the necessary includes and set up the variables. */
#include
/* Create an unnamed socket for the server. */
server_sockfd = socket(AF_INET, SOCK_STREAM, 0); /* Name the socket. */
server_address.sin_family = AF_INET; server_address.sin_addr.s_addr = inet_addr("127.0.0.1"); server_address.sin_port = 9734; server_len = sizeof(server_address); bind(server_sockfd, (struct sockaddr *)&server_address, server_len);
/* Create a connection queue and wait for clients. */
listen(server_sockfd, 5); while(1) { char ch;
printf("server waiting\n");
/* Accept a connection. */
client_len = sizeof(client_address); client_sockfd = accept(server_sockfd, (struct sockaddr *)&client_address, &client_len);
/* We can now read/write to client on client_sockfd. */
read(client_sockfd, &ch, 1); ch++; write(client_sockfd, &ch, 1); close(client_sockfd); } } client2.c //domain socket
/* Make the necessary includes and set up the variables. */
#include
/* Create a socket for the client. */
sockfd = socket(AF_INET, SOCK_STREAM, 0);
/* Name the socket, as agreed with the server. */
address.sin_family = AF_INET; address.sin_addr.s_addr = inet_addr("127.0.0.1"); address.sin_port = 9734; len = sizeof(address);
/* Now connect our socket to the server's socket. */
result = connect(sockfd, (struct sockaddr *)&address, len);
if(result == -1) { perror("oops: client2"); exit(1); }
/* We can now read/write via sockfd. */
write(sockfd, &ch, 1); read(sockfd, &ch, 1); printf("char from server = %c\n", ch); close(sockfd); exit(0); }
UNIX domain sockets sc.h #include
#define SERVER "/tmp/server" unixDomainSocketServer.c
#include
signal (SIGINT, stop) ; signal (SIGQUIT, stop) ; signal (SIGTERM, stop) ;
if ((sock_fd = socket (AF_UNIX, SOCK_STREAM, 0)) < 0) { perror ("srv: socket ()") ; exit (1) ; }
unix_addr.sun_family = AF_UNIX ; strcpy (unix_addr.sun_path, SERVER) ; addr_len = sizeof (unix_addr.sun_family) + strlen (unix_addr.sun_path) ; unlink (SERVER) ;
if (bind (sock_fd, (struct sockaddr *) &unix_addr, addr_len) < 0) { perror ("srv: bind ()") ; exit (1) ; }
if (listen (sock_fd, 5) < 0) { perror ("srv: client ()") ; exit (1) ; } while ((cli_sock_fd = accept (sock_fd, (struct sockaddr *) &unix_addr , &addr_len)) >= 0) { if ((n = read (cli_sock_fd, buf, 2047)) < 0) { perror ("srv: read ()") ; close (cli_sock_fd) ; continue ; }
buf[n] = '\0' ; for (pc = buf ; *pc != '\0' && (*pc < '0' || *pc > '9') ; pc ++) ;
pid = atoi (pc) ; if (pid != 0) { sprintf (buf, "Hello Client %d, this is the Server.\n", pid) ; n = strlen (buf) + 1 ;
if (write (cli_sock_fd, buf, n) != n) perror ("srv: write ()") ; }
close (cli_sock_fd) ; }
perror ("srv: accept ()") ; unlink (SERVER) ; exit (1) ; } int main (void) { int r ; if ((r = fork ()) == 0) { server () ; }
if (r < 0) { perror ("srv: fork ()") ; exit (1) ; }
exit (0) ; } unixDomainCLient.c
#include "sc.h" int main (void) { int sock_fd ; struct sockaddr_un unix_addr ; char buf[2048] ; int n ;
if ((sock_fd = socket (AF_UNIX, SOCK_STREAM, 0)) < 0) { perror ("cli: socket ()") ; exit (1) ; }
unix_addr.sun_family = AF_UNIX ; strcpy (unix_addr.sun_path, SERVER) ;
if (connect (sock_fd, (struct sockaddr *) &unix_addr , sizeof (unix_addr.sun_family) + strlen (unix_addr.sun_path)) < 0) { perror ("cli: connect ()") ; exit (1) ; }
sprintf (buf, "Hello Server, this is %d.\n", getpid ()) ; n = strlen (buf) + 1 ; if (write (sock_fd, buf, n) != n) { perror ("cli: write ()") ; exit (1) ; }
if ((n = read (sock_fd, buf, 2047)) < 0) { perror ("cli: read ()") ; exit (1) ; }
buf[n] = '\0' ; printf ("Client received: %s\n", buf) ;
exit (0) ; } variableArguments.c
#include
int maxof(int n_args, ...){ register int i; int max, a; va_list ap;
va_start(ap, n_args); max = va_arg(ap, int); for(i = 2; i <= n_args; i++) { if((a = va_arg(ap, int)) > max) max = a; }
va_end(ap); return max; } void f(void) { int i = 5; int j[256]; j[42] = 24; printf("%d\n",maxof(3, i, j[42], 0));
}
Windows Sockets
You need to include ws32_32.lib at the end of link property of the Project settings
WinSockStreamServer.c
#include
// Winsock initialization WSAStartup(MAKEWORD(2, 0), &wsaData);
// Winsock object creation sockSvr = socket(AF_INET, SOCK_STREAM, 0);
// Winsock server configuration addrSockSvr.sin_family = AF_INET; addrSockSvr.sin_port = htons(6060); addrSockSvr.sin_addr.S_un.S_addr = INADDR_ANY; bind(sockSvr, (struct sockaddr *)&addrSockSvr, sizeof(addrSockSvr));
// Listening at the port listen(sockSvr, 5);
while(1) { // Receiving client request nlen = sizeof(addrSockclt); sockSS = accept(sockSvr, (struct sockaddr *)&addrSockclt, &nlen);
// Sending message to the client printf("Connection from %s (port no. : %d)\n", inet_ntoa(addrSockclt.sin_addr), //IP address ntohs(addrSockclt.sin_port)); // Port Number send(sockSS, "Hello TCP/IP world", 18, 0);
// TCP session end closesocket(sockSS); }
// Winsock object cleanup WSACleanup();
getchar();
return 0; }
WinSockStreamCLient.c
#include
WSADATA wsaData; SOCKET sockClt; char szMsg[32]; struct sockaddr_in addrSockSvr; int nLet;
//Winsock Initialization WSAStartup(MAKEWORD(2, 0), &wsaData);
// Create Winsock Object sockClt = socket(AF_INET, SOCK_STREAM, 0); // Server Configuration for the Winsock object addrSockSvr.sin_family = AF_INET; addrSockSvr.sin_port = htons(6060); addrSockSvr.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");
// Connect to the server connect(sockClt, (struct sockaddr *)&addrSockSvr, sizeof(addrSockSvr));
// receive data from socket memset(szMsg, 0, sizeof(szMsg)); nLet = recv(sockClt, szMsg, sizeof(szMsg), 0);
printf("%s\n", szMsg);
// Cleanup Winsock object WSACleanup();
getchar(); return 0; }