1,文件的读写
0号文件描述符—标准输入，1号文件描述符—标准输出，2号文件描述符—标准错误
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#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
int main()
{
int srcFile,desFile;
char *srcPath = "/home/phinecos/hello.c";//source file
char *desPath = "/home/phinecos/hello_back.c";//dest file
srcFile = open(srcPath,O_RDONLY);//open source file
if(srcFile==-1)
{//open source file failed
write(2,"open err\n",9);
return -1;
}
desFile = open(desPath,O_CREAT|O_WRONLY,S_IRUSR|S_IWUSR);//open dest file
if(desFile==-1)
{//open dest file failed
write(2,"open err\n",9);
return -1;
}
char buffer[256];
int nReaded;
while((nReaded=read(srcFile,buffer,256))>0)
{//read source into buffer,then write buffer into dest
write(desFile,buffer,nReaded);
}
close(srcFile);//close source file
close(desFile);//close dest file
return 0;
}
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2，lstat和stat的区别是当文件是一个符合链接时，lstat返回链接本身的信息，而stat返回的是链接所指向的文件的信息。
3，遍历一个目录
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#include <unistd.h>
#include <stdio.h>
#include <dirent.h>
#include <string.h>
#include <sys/stat.h>
void printdir(char *dir, int depth)
{
DIR *dp;
struct dirent *entry;
struct stat statbuf;
if((dp = opendir(dir)) == NULL) {
fprintf(stderr,"cannot open directory: %s\n", dir);
return;
}
chdir(dir);
while((entry = readdir(dp)) != NULL) {
lstat(entry->d_name,&statbuf);
if(S_ISDIR(statbuf.st_mode)) {
/* Found a directory, but ignore . and .. */
if(strcmp(".",entry->d_name) == 0 ||
strcmp("..",entry->d_name) == 0)
continue;
printf("%*s%s/\n",depth,"",entry->d_name);
/* Recurse at a new indent level */
printdir(entry->d_name,depth+4);
}
else printf("%*s%s\n",depth,"",entry->d_name);
}
chdir("..");
closedir(dp);
}
/* Now we move onto the main function. */
int main()
{
printf("Directory scan of /home:\n");
printdir("/home",0);
printf("done.\n");
exit(0);
}
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4，内存映射文
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#include <unistd.h>
#include <stdio.h>
#include <sys/mman.h>
#include <fcntl.h>
//记录结构体
typedef struct
{
int integer;//标号
char string[24];//名称
} RECORD;
#define NRECORDS (100)
int main()
{
RECORD record, *mapped;
int i, f;
FILE *fp;
fp = fopen("records.dat","w+");
for(i=0; i<NRECORDS; i++)
{
record.integer = i;
sprintf(record.string,"RECORD-%d",i);
fwrite(&record,sizeof(record),1,fp);
}
fclose(fp);
/* We now change the integer value of record 43 to 143
and write this to the 43rd record's string. */
fp = fopen("records.dat","r+");
fseek(fp,43*sizeof(record),SEEK_SET);
fread(&record,sizeof(record),1,fp);
record.integer = 143;
sprintf(record.string,"RECORD-%d",record.integer);
fseek(fp,43*sizeof(record),SEEK_SET);
fwrite(&record,sizeof(record),1,fp);
fclose(fp);
/* We now map the records into memory
and access the 43rd record in order to change the integer to 243
(and update the record string), again using memory mapping. */
f = open("records.dat",O_RDWR);
mapped = (RECORD *)mmap(0, NRECORDS*sizeof(record), PROT_READ|PROT_WRITE, MAP_SHARED, f, 0);
mapped[43].integer = 243;
sprintf(mapped[43].string,"RECORD-%d",mapped[43].integer);
msync((void *)mapped, NRECORDS*sizeof(record), MS_ASYNC);
munmap((void *)mapped, NRECORDS*sizeof(record));
close(f);
exit(0);
}
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本文转自Phinecos(洞庭散人)博客园博客，原文链接：http://www.cnblogs.com/phinecos/archive/2008/11/24/1340071.html，如需转载请自行联系原作者
