Linux下对文件的某一记录进行上锁

 

 

/*************************************************************        FileName : LockFile.c    FileFunc : 实现文件的记录锁,对文件中的值进行加1      Version  : V0.1        Author   : Study      Date     : 2012-05-11    Descp    : Linux下对文件的某一记录进行上锁   *************************************************************/#include <stdio.h>#include <string.h>#include <fcntl.h>#include <errno.h>#include <sys/stat.h>int LockInit(char *pathname);int  LockWait();intLockRelease();long GetLocalSerial(char* ptrLocalSerial);#define FILE_MODE (S_IRUSR|S_IWUSR|S_IRGRP|S_IROTH)static struct flocklock_it, unlock_it;static int lock_fd = -1;int LockInit(char *pathname){char lock_file[150];memset(lock_file,0,sizeof(lock_file));strncpy(lock_file,pathname,sizeof(lock_file));mkstemp(lock_file);if((lock_fd=open(lock_file,O_CREAT|O_WRONLY,FILE_MODE))<0){    perror("open");    return -1;}printf("LockInit:lock_fd = %d \n",lock_fd);unlink(lock_file);lock_it.l_type=F_WRLCK;lock_it.l_whence=SEEK_SET;lock_it.l_start=0;lock_it.l_len=0;unlock_it.l_type=F_UNLCK;unlock_it.l_whence=SEEK_SET;unlock_it.l_start=0;unlock_it.l_len=0;return 0;}int  LockWait(){intrc;while((rc=fcntl(lock_fd,F_SETLKW,&lock_it))<0){printf("LockWait:rc = %d \n",rc);if(errno==EINTR)continue;elsereturn -1;}return 0;}int LockRelease(){if(fcntl(lock_fd, F_SETLKW, &unlock_it)<0)return -1;return 0;}long GetLocalSerial(char* ptrLocalSerial){char tmp1[100];char buf[100];int fd,iRetCode;long iMaxSerial;memset(tmp1,0,sizeof(tmp1));//sprintf(tmp1,"%s/etc/serialfile",getenv("HOME"));sprintf(tmp1,"%s/serialfile",getenv("PWD"));printf("tmp1 = %s \n",tmp1);LockInit("./tmp");fd=open(tmp1,O_RDWR);printf("GetLocalSerial:fd = %d \n",fd);memset(buf,0,sizeof(buf));iRetCode=LockWait();printf("GetLocalSerial:iRetCode = %d \n",iRetCode);read(fd,buf,6);iMaxSerial=strtol(buf,0,10)+1;if(iMaxSerial==999999)iMaxSerial=0;sprintf(ptrLocalSerial,"%06ld",iMaxSerial);lseek(fd,0,0);write(fd,ptrLocalSerial,6);close(fd);iRetCode=LockRelease();return iMaxSerial;}int main(int argc,char *argv[]){long lSerialNumber;char szSerialNumber[30];memset(szSerialNumber,0,sizeof(szSerialNumber));lSerialNumber = GetLocalSerial(szSerialNumber);printf("lSerialNumber = %d \n",lSerialNumber);return 0;}