linux修改程序的配置文件

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
 
int main(int argc, char **argv)
{
    int fdSrc;
    char *readBuf=NULL;
 
    if(argc != 2){
        printf("pararm error\n");
        exit(-1);
    }
    
    fdSrc = open(argv[1],O_RDWR);
    int size = lseek(fdSrc,0,SEEK_END);
    lseek(fdSrc,0,SEEK_SET);
 
    readBuf=(char *)malloc(sizeof(char)*size + 8);
 
    int n_read = read(fdSrc, readBuf, size);
    
    char *p = strstr(readBuf,"LENG=");
    if(p==NULL){
        printf("not found\n");
        exit(-1);
    }
    
    p = p+strlen("LENG=");
    *p = '7';
    
    lseek(fdSrc,0,SEEK_SET);
    int n_write = write(fdSrc,readBuf,strlen(readBuf));
    
    close(fdSrc);
 
    return 0;
}