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
", errMsg, strerror(errno));
    exit(-1);
}

long getFileSize1(FILE *fp)
{
    if (fseek(fp, 0, SEEK_END) != 0)
    {
        errHandling("fseek() fail");
    }    
    return ftell(fp);
}

long getFileSize2(int fd)
{
    struct stat st;
    if ((fstat(fd, &st)) != 0)
    {
        errHandling("fstat() fail");
    }
    return st.st_size;
}

int main(int argc, char *argv[])
{
    if (argc != 2)
    {
        printf("Usage: %s <file_name>
", argv[0]);
        exit(-1);        
    }
    
    FILE *fp = fopen(argv[1], "r");
    if (NULL == fp)
    {
        errHandling("open() fail");
    }
    
    printf("The size of %s: %ld bytes (fseek+ftell)
", argv[1], getFileSize1(fp));
    printf("The size of %s: %ld bytes (fstat)
", argv[1], getFileSize2(fileno(fp)));
    
    fclose(fp);
    exit(0);
}

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
", errMsg, strerror(errno));
    exit(-1);
}

long getFileSize(int fd)
{
    struct stat st;
    if ((fstat(fd, &st)) != 0)
    {
        errHandling("fstat() fail");
    }
    return st.st_size;
}

/* in sequence */
unsigned long getReadTimeSeq(char *pbuf, FILE *pf)
{
    int readCnt = 0;
    struct timeval bgn;
    struct timeval end;
    unsigned long timeCnt = 0;
    
    memset(&bgn, 0, sizeof(struct timeval));
    memset(&end, 0, sizeof(struct timeval));
    printf("Start read in sequence
");
    gettimeofday(&bgn, NULL);
    while (readCnt < READ_SIZE)
    {
        memset(pbuf, 0, BUF_SIZE);
        readCnt += fread(pbuf, 1, BUF_SIZE, pf);
        //printf("read %d MB
", readCnt >> 20);
    }
    gettimeofday(&end, NULL);
    return ((end.tv_sec - bgn.tv_sec) * 1000000 + (end.tv_usec - bgn.tv_usec));
}

/* inverted sequence */
unsigned long getReadTimeInvertSeq(char *pbuf, FILE *pf)
{
    int readCnt = 0;
    long shift = READ_SIZE - BUF_SIZE;
    struct timeval bgn;
    struct timeval end;
    unsigned long timeCnt = 0;

    memset(&bgn, 0, sizeof(struct timeval));
    memset(&end, 0, sizeof(struct timeval));
    //printf("Start read in inverted sequence
");
    gettimeofday(&bgn, NULL);
    while (readCnt < READ_SIZE)
    {
        fseek(pf, shift, SEEK_SET);
        memset(pbuf, 0, BUF_SIZE);
        readCnt += fread(pbuf, 1, BUF_SIZE, pf);
        shift -= readCnt;
        //printf("read %d MB
", readCnt >> 20);
    }
    gettimeofday(&end, NULL);
    return ((end.tv_sec - bgn.tv_sec) * 1000000 + (end.tv_usec - bgn.tv_usec));
}

/* Random sequence */
unsigned long getReadTimeRandPos(char *pbuf, FILE *pf)
{
    int readCnt = 0;
    long shift = READ_SIZE - BUF_SIZE;
    struct timeval bgn;
    struct timeval end;
    unsigned long timeCnt = 0;

    memset(&bgn, 0, sizeof(struct timeval));
    memset(&end, 0, sizeof(struct timeval));
    srand((int)time(0));
    //int num = 0;
    gettimeofday(&bgn, NULL);
    while (readCnt < READ_SIZE)
    {
        //++num;
        shift = BUF_SIZE * (rand() % NUM_ROUND);
        fseek(pf, shift, SEEK_SET);
        memset(pbuf, 0, BUF_SIZE);
        readCnt += fread(pbuf, 1, BUF_SIZE, pf);
    }
    gettimeofday(&end, NULL);
    //printf("num = %d
", num);
    return ((end.tv_sec - bgn.tv_sec) * 1000000 + (end.tv_usec - bgn.tv_usec));
}

int main(int argc, char *argv[])
{
    if (argc != 2)
    {
        printf("Usage: %s <file_name>
", argv[0]);
        exit(-1);        
    }
    
    FILE *pf = fopen(argv[1], "w+");
    if (NULL == pf)
    {
        errHandling("open() fail");
    }
    /*生成大小为1G的文件*/
    fseek(pf, READ_SIZE, SEEK_SET);
    fputc(166, pf);
    rewind(pf);

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

    printf("Time in sequence: timeCnt = %ld us
", getReadTimeSeq(buf, pf));    
    printf("Time in inverted sequence: timeCnt = %ld us
", getReadTimeInvertSeq(buf, pf));
    printf("Time in random sequence: timeCnt = %ld us
", getReadTimeRandPos(buf, pf));
    
    fclose(pf);
    free(buf);
    exit(0);
}

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