fopen & fcolse & fseek & ftell & fstat 文件操作函数测试

1、文件大小查询file_size.c

　　方法一：fseek + ftell；

　　方法二：ftell

 #include <stdio.h>
 #include <fcntl.h>
 #include <stdlib.h>
 #include <string.h>
 #include <errno.h>

 void errHandling(const char *errMsg)
 {
     printf("%s: %s\n", errMsg, strerror(errno));
     exit(-);
 }

 long getFileSize1(FILE *fp)
 {
     if (fseek(fp, , SEEK_END) != )
     {
         errHandling("fseek() fail");
     }
     return ftell(fp);
 }

 long getFileSize2(int fd)
 {
     struct stat st;
     if ((fstat(fd, &st)) != )
     {
         errHandling("fstat() fail");
     }
     return st.st_size;
 }

 int main(int argc, char *argv[])
 {
     if (argc != )
     {
         printf("Usage: %s <file_name>\n", argv[]);
         exit(-);
     }

     FILE *fp = fopen(argv[], "r");
     if (NULL == fp)
     {
         errHandling("open() fail");
     }

     printf("The size of %s: %ld bytes (fseek+ftell)\n", argv[], getFileSize1(fp));
     printf("The size of %s: %ld bytes (fstat)\n", argv[], getFileSize2(fileno(fp)));

     fclose(fp);
     exit();
 }

2、特定大小文件创建以及读取操作时间测试 read_file_time.c

　　描述：创建1G大小文件，并完成顺序、逆序以及随机读取操作

 #include <stdio.h>
 #include <fcntl.h>
 #include <stdlib.h>
 #include <string.h>
 #include <errno.h>
 #include <sys/time.h>

 #define BUF_SIZE (1024 * 1024)
 #define READ_SIZE (BUF_SIZE * 1024)
 #define NUM_ROUND 1024

 void errHandling(const char *errMsg)
 {
     printf("%s: %s\n", errMsg, strerror(errno));
     exit(-);
 }

 long getFileSize(int fd)
 {
     struct stat st;
     if ((fstat(fd, &st)) != )
     {
         errHandling("fstat() fail");
     }
     return st.st_size;
 }

 /* in sequence */
 unsigned long getReadTimeSeq(char *pbuf, FILE *pf)
 {
     int readCnt = ;
     struct timeval bgn;
     struct timeval end;
     unsigned long timeCnt = ;

     memset(&bgn, , sizeof(struct timeval));
     memset(&end, , sizeof(struct timeval));
     printf("Start read in sequence\n");
     gettimeofday(&bgn, NULL);
     while (readCnt < READ_SIZE)
     {
         memset(pbuf, , BUF_SIZE);
         readCnt += fread(pbuf, , BUF_SIZE, pf);
         //printf("read %d MB\n", readCnt >> 20);
     }
     gettimeofday(&end, NULL);
     return ((end.tv_sec - bgn.tv_sec) *  + (end.tv_usec - bgn.tv_usec));
 }

 /* inverted sequence */
 unsigned long getReadTimeInvertSeq(char *pbuf, FILE *pf)
 {
     int readCnt = ;
     long shift = READ_SIZE - BUF_SIZE;
     struct timeval bgn;
     struct timeval end;
     unsigned long timeCnt = ;

     memset(&bgn, , sizeof(struct timeval));
     memset(&end, , sizeof(struct timeval));
     //printf("Start read in inverted sequence\n");
     gettimeofday(&bgn, NULL);
     while (readCnt < READ_SIZE)
     {
         fseek(pf, shift, SEEK_SET);
         memset(pbuf, , BUF_SIZE);
         readCnt += fread(pbuf, , BUF_SIZE, pf);
         shift -= readCnt;
         //printf("read %d MB\n", readCnt >> 20);
     }
     gettimeofday(&end, NULL);
     return ((end.tv_sec - bgn.tv_sec) *  + (end.tv_usec - bgn.tv_usec));
 }

 /* Random sequence */
 unsigned long getReadTimeRandPos(char *pbuf, FILE *pf)
 {
     int readCnt = ;
     long shift = READ_SIZE - BUF_SIZE;
     struct timeval bgn;
     struct timeval end;
     unsigned long timeCnt = ;

     memset(&bgn, , sizeof(struct timeval));
     memset(&end, , sizeof(struct timeval));
     srand((int)time());
     //int num = 0;
     gettimeofday(&bgn, NULL);
     while (readCnt < READ_SIZE)
     {
         //++num;
         shift = BUF_SIZE * (rand() % NUM_ROUND);
         fseek(pf, shift, SEEK_SET);
         memset(pbuf, , BUF_SIZE);
         readCnt += fread(pbuf, , BUF_SIZE, pf);
     }
     gettimeofday(&end, NULL);
     //printf("num = %d\n", num);
     return ((end.tv_sec - bgn.tv_sec) *  + (end.tv_usec - bgn.tv_usec));
 }

 int main(int argc, char *argv[])
 {
     if (argc != )
     {
         printf("Usage: %s <file_name>\n", argv[]);
         exit(-);
     }

     FILE *pf = fopen(argv[], "w+");
     if (NULL == pf)
     {
         errHandling("open() fail");
     }
     /*生成大小为1G的文件*/
     fseek(pf, READ_SIZE, SEEK_SET);
     fputc(, pf);
     rewind(pf);

     char *buf = (char *)malloc(BUF_SIZE * sizeof(char));
     if (NULL == buf)
     {
         errHandling("malloc() fail");
     }

     printf("Time in sequence: timeCnt = %ld us\n", getReadTimeSeq(buf, pf));
     printf("Time in inverted sequence: timeCnt = %ld us\n", getReadTimeInvertSeq(buf, pf));
     printf("Time in random sequence: timeCnt = %ld us\n", getReadTimeRandPos(buf, pf));

     fclose(pf);
     free(buf);
     exit();
 }

3、编译

EXES := read size

.PHONY : all
all : $(EXES)

read : read_file_time.o
    gcc -o read read_file_time.o
read_file_time.o : read_file_time.c
    gcc -c read_file_time.c

size : file_size.o
    gcc -o size file_size.o
file_size.o : file_size.c
    gcc -c file_size.c

clean :
    rm -f *.o $(EXES)

　　统一编译以上两个源文件，并生成两个对应的可执行文件