原文地址：
感觉linux环境下C编程主要是一堆库函数的调用。
一.关于linux进程控制
关于进程的创建。
linux中fork()和vfork()函数可以创建一个子进程。
其中vfork()创建的子进程与父进程共享数据，仅子进程先与父进程运行。
代码：fork()创建子进程
#include "unistd.h"#include "stdio.h"main(){ pid_t result; result = fork(); if(result == -1) printf("error"); else if(result == 0) printf("\n\nresult:%d\nin child process\npid:%d\n\n",result,getpid()); else printf("result:%d\nin father process\npid:%d",result,getpid());} 
代码：由于vfork()创建的子进程与父进程共享数据
#include "stdio.h"#include "unistd.h"main(){ pid_t pid; int count = 0; pid = vfork(); count++; if(pid == -1) printf("error"); else if(pid == 0) printf("in child process count is:%d\n",count); else printf("in father process count is:%d\n",count);} 
关于exec函数族
exec函数族，可以在一个进程中启动另一个程序，当该进程不能为系统和用过贡献时，可以调用exec族函数执行另一个程序。
代码：execl调用编译后的helloworld.c文件
#include "stdio.h"#include "unistd.h"main(){ if(execl("/home/he/program/ctest/helloworld",NULL)<0) printf("error\n");} 
关于wait()与waitpid()函数。
wait()与waitpid可以阻塞父进程。
pid_t wait(int *status)
waitpid原型
代码：waitpid使用
#include "unistd.h"#include "stdio.h"#include "sys/types.h"#include "sys/wait.h"main(){ pid_t result; int pr; result = fork(); if(result == -1) printf("error\n"); else if(result == 0) { sleep(5); printf("\n\nresult:%d\nin child process\npid:%d\n\n",result,getpid()); } else { while(!(pr=waitpid(result,NULL,WNOHANG))) { sleep(1); printf("the child process not exit\n"); } printf("result:%d\nin father process\npid:%d\n\n",result,getpid()); }} 
关于linux守护进程
守护进程是linux后台服务进程，该进程独立于终端，周期性执行某种任务。
代码：编写守护进程
#include#include #include #include #include #include #include #include #define MAXFILE 65535int main(){ pid_t pc,sid; int i,fd,len; char *buf="This is a Dameon\n"; len =strlen(buf); pc=fork(); if(pc<0) { printf("error fork\n"); exit(1); }else if(pc>0) exit(0); openlog("demo_update",LOG_PID, LOG_DAEMON); if((sid=setsid())<0) { syslog(LOG_ERR, "%s\n", "setsid"); exit(1); } if((sid=chdir("/"))<0) { syslog(LOG_ERR, "%s\n", "chdir"); exit(1); } umask(0); for(i=0;i
该进程会10s周期向目标文件写入数据。
二.进程件的通讯
关于管道通讯
#include#include #include #include int main(){ int pipe_fd[2],New_process_result; char send_data[] = "This a message from father process"; char receive_data[100]; if(pipe(pipe_fd)<0) { printf("pipe create error\n"); } else printf("pipe create success\n"); if((New_process_result=fork()) == -1) { printf("Fork error\n"); } else if(New_process_result == 0)//子进程 { sleep(1); read(pipe_fd[0],receive_data,100); printf("%s",receive_data); putchar('\n'); } else//父进程 { write(pipe_fd[1],send_data,strlen(send_data)); sleep(2); }}
在子进程中，打印父进程写入的数据。
关于FIFO有名管道
pipe管道只能用于父子进程通讯。
FIFO可以用于任意两个进程间的通讯。
fifo_write.c 写数据文件
#include#include #include #include #include #include #include #define FIFO_SERVER "/tmp/myfifo"main(int argc,char** argv){ int fd; char w_buf[100]; char exitflag[] = "exit"; int nwrite; fd = open(FIFO_SERVER,O_RDWR|O_NONBLOCK,0); if(fd==-1) { perror("open error"); exit(1); } else printf("open success\n"); while(1) { scanf("%s",&w_buf[0]); if((nwrite=write(fd,w_buf,100))==-1) { if(errno==EAGAIN) printf("The FIFO has not been read yet.Please try later\n"); } else printf("write %s to the FIFO\n",w_buf); if(!(strcmp(w_buf,exitflag))) exit(1); }}
fifo_read读数据文件
#include#include #include #include #include #include #include #define FIFO "/tmp/myfifo"main(int argc,char** argv){ char buf_r[100]; char exitflag[] = "exit"; int fd; int nread; if((mkfifo(FIFO,O_CREAT|O_EXCL)<0)&&(errno!=EEXIST)) printf("cannot create fifoserver\n"); printf("Preparing for reading bytes...\n"); memset(buf_r,0,sizeof(buf_r)); fd=open(FIFO,O_RDONLY|O_NONBLOCK,0); if(fd==-1) { perror("open"); exit(1); } while(1) { memset(buf_r,0,sizeof(buf_r)); read(fd,buf_r,100); if(buf_r[0] == '\0') ; else if(!strcmp(buf_r,exitflag)) exit(1); else printf("read %s from FIFO\n",buf_r); } pause(); unlink(FIFO); }
在两个不同的终端中运行结果：
exit退出程序。
关于信号
代码：signal键入信号（ctrl C）信号处理函数：sigint_handler
#include "stdio.h"#include "signal.h"#include "stdlib.h"void sigint_handler(int sign_num){ if(sign_num == SIGINT) printf("\n\"SIGINT\" singal\n");}int main(){ signal(SIGINT,sigint_handler); pause();} 
代码sigaction函数
#include "stdio.h"#include "signal.h"#include "stdlib.h"void sigint_handler(int sign_num){ if(sign_num == SIGINT) printf("\n\"SIGINT\" singal\n");}int main(){ struct sigaction my_signal; my_signal.sa_handler = sigint_handler; sigemptyset(&my_signal.sa_mask); my_signal.sa_flags = 0; sigaction(SIGINT,&my_signal,0); pause();} 代码：父进程发生信号杀死子进程
#include#include #include #include #include int main(){ pid_t pid; if((pid=fork())<0) { perror("fork"); exit(1); } if(pid == 0) //子进程 { while(1) { printf("child process runing\n"); sleep(1); } } else //父进程 { int count; for(count=0;count<5;count++) { sleep(1); printf("father process runing\n"); } if((count = kill(pid,SIGKILL)) == 0) { printf("\n\nfather process kill:%d\n",pid); } }}
关于信号量
同uc/os-II信号量用于对共享资源的标记
sem_com.h文件 信号量操作
#include "stdio.h"#include "unistd.h"#include "stdlib.h"#include "sys/types.h"#include "sys/ipc.h"#include "sys/shm.h"#include "sys/sem.h"extern int init_sem( int sem_id, int init_value );extern int del_sem( int sem_id );extern int sem_p( int sem_id );extern int sem_v( int sem_id );union semun{ int val; struct semid_ds *buf; unsigned short *array; //struct seminfo *_buf;}; sem_com.c文件
#include "sem_com.h"int init_sem( int sem_id, int init_value ){ union semun sem_union; sem_union.val = init_value; if ( semctl(sem_id, 0, SETVAL, sem_union) == -1 ) { perror( "initialize semaphore" ); return(-1); } return(0);}int del_sem( int sem_id ){ union semun sem_union; if ( semctl(sem_id, 0,IPC_RMID, sem_union) == -1 ) { perror( "Delete semaphore" ); return(-1); } return(0);}int sem_p( int sem_id ){ struct sembuf sem_b; sem_b.sem_num = 0; /* id */ sem_b.sem_op = -1; /* P operation */ sem_b.sem_flg = SEM_UNDO; if ( semop(sem_id, &sem_b, 1) == -1 ) { perror( "P operation" ); return(-1); } return 0;}int sem_v( int sem_id ){ struct sembuf sem_b; sem_b.sem_num = 0; /* id */ sem_b.sem_op = 1; /* V operation */ sem_b.sem_flg = SEM_UNDO; if ( semop(sem_id, &sem_b, 1) == -1 ) { perror( "V operation" ); return(-1); } return 0;} 主函数main.c文件
#include "sem_com.h"int main(){ pid_t result; int sem_id; sem_id = semget(1,1,0666|IPC_CREAT); init_sem(sem_id, 0); sem_v(sem_id); result = fork(); if(result == -1) printf("error"); else if(result == 0) //子进程 { sem_p(sem_id); printf("child process get sem\n"); sem_v(sem_id); } else //父进程 { sem_p(sem_id); printf("father process get sem\n"); sleep(3); printf("father process used sem\n"); sem_v(sem_id); sleep(1); } exit(0);} 由于父进程先运行子进程无法获取信号量，在父进程sleep中，子进程依然无法运行。
关于共享内存
由shmget函数创建共享内存shmat函数映射共享内存地址。
代码：由父进程写入共享内存，子进程读取。
#include#include #include #include #include int main(){ int shmid,process_ret; char *shmadd; if((shmid=shmget(IPC_PRIVATE, 1024, 0666))<0) { perror("shmget"); exit(1); } if((process_ret = fork()) == -1) printf("process creat error\n"); else if(process_ret == 0)//子进程 { sleep(2); printf("in child process\n"); if((shmadd=shmat(shmid,0,0)) == (void*)(-1)) { perror("shmat"); exit(1); } //shmadd = "acc";不能这么干，shmadd地址改变了。 shmadd[0] = 'A'; printf("In child process:%s\n",shmadd); if((shmdt(shmadd))<0) { perror("shmdt"); exit(1); } } else //父进程 { char share_message[] = " this is share context from father process"; int count; printf("in father process\n"); if((shmadd=shmat(shmid,0,0)) == (void *)(-1)) { perror("shmat"); exit(1); } for(count=0;share_message[count]!='\0';count++) shmadd[count] = share_message[count]; if((shmdt(shmadd))<0) { perror("shmdt"); exit(1); } sleep(10); }}
消息队列
1 #include2 #include 3 #include 4 #include 5 #include 6 #include 7 #include 8 9 struct message10 {11 long msg_type;12 char msg_text[512];13 };14 15 int main()16 {17 int qid;18 key_t key;19 int len;20 struct message msg;21 char a[100];22 23 if((key=ftok(".",'a'))==-1)24 {25 perror("ftok");26 exit(1);27 }28 if((qid=msgget(key,IPC_CREAT|0666))==-1) //创建消息列对29 {30 perror("msgget");31 exit(1);32 }33 printf("Please send a message:");34 35 scanf("%s",&msg.msg_text[0]);36 37 msg.msg_type = getpid();38 39 len = strlen(msg.msg_text);40 41 if((msgsnd(qid,&msg,len,0))<0) //发送消息42 {43 perror("message posted");44 exit(1);45 }46 47 if(msgrcv(qid,&msg,BUFSZ,0,0)<0) //接受消息48 {49 perror("msgrcv");50 exit(1);51 }52 53 printf("message is:%s\n",&msg.msg_text[0]); //删除消息54 55 if((msgctl(qid,IPC_RMID,NULL))<0)56 {57 perror("msgctl");58 exit(1);59 }60 exit(0);61 }
三.关于线程
linux的线程，类似于uC/os-II中的“任务”。
进程的创建
#include "stdio.h"#include "pthread.h"#include "stdlib.h"void thread_one(void){ int i; for(i=0;i<10;i++) printf("thread one is runing\n");}void thread_two(void){ int i; sleep(1); for(i=0;i<10;i++) printf("thread two is runing\n"); }main(){ pthread_t thread_one_id,thread_two_id; int resurt; if((resurt = pthread_create(&thread_one_id, NULL, (void *)thread_one, NULL))== -1) { printf("thread one creat error\n"); exit(1); } if((resurt = pthread_create(&thread_two_id, NULL, (void *)thread_two, NULL))== -1) { printf("thread two creat error\n"); exit(1); } pthread_join(thread_one_id, NULL); pthread_join(thread_two_id, NULL);} 进程有多个属性。（优先级，分离，绑定……）
可通过相应的函数设置创建相应属性进程。
创建优先级为11，时间片轮转调度，绑定，分离属性的进程
thread_one_priority = 11; pthread_attr_init(&thread_one_attr); pthread_attr_setinheritsched(&thread_one_attr, PTHREAD_EXPLICIT_SCHED); pthread_attr_setschedpolicy(&thread_one_attr, SCHED_RR); pthread_attr_setschedparam(&thread_one_attr, (struct sched_param *)&thread_one_priority); pthread_attr_setscope(&thread_one_attr, PTHREAD_SCOPE_SYSTEM); pthread_attr_setdetachstate(&thread_one_attr,PTHREAD_CREATE_DETACHED); if((resurt = pthread_create(&thread_one_id, &thread_one_attr, (void *)thread_one, NULL))) { printf("thread one creat error\n"); exit(1); }
互斥锁使用
#include "stdio.h"#include "stdlib.h"#include "pthread.h"pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;void thread_one(void){ printf("thread_one attempt lock\n"); pthread_mutex_lock(&mutex); printf("thead_one lock success\n"); sleep(2); printf("thread_one is runing\n"); printf("thread_one unlock\n"); pthread_mutex_unlock(&mutex);}void thread_two(void){ sleep(1); printf("thread_two attempt lock\n"); pthread_mutex_lock(&mutex); printf("thead_two lock success\n"); printf("thread_two is runing\n"); printf("thread_two unlock\n"); pthread_mutex_unlock(&mutex);}main(){ pthread_t thread_one_id,thread_two_id; int resurt; pthread_mutex_init(&mutex,NULL); if((resurt = pthread_create(&thread_one_id, NULL, (void *)thread_one, NULL))== -1) { printf("thread one creat error\n"); exit(1); } if((resurt = pthread_create(&thread_two_id, NULL, (void *)thread_two, NULL))== -1) { printf("thread two creat error\n"); exit(1); } pthread_join(thread_one_id, NULL); pthread_join(thread_two_id, NULL);}
由于使用互斥锁，进程2等待进程1解锁，才能运行。
