49 lines
792 B
C
49 lines
792 B
C
#include<stdio.h>
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#include<fcntl.h>
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#include<unistd.h>
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#include<stdlib.h>
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#include<string.h>
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#define szbuf 256
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int main(int argc, char const *argv[])
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{
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char buf[szbuf];
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int fd, l, n, x;
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long int i, offset;
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if(argc<3)
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{
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fprintf(stderr, "Usage: %s ./get_numb <file_name> <offset>",argv[1]);
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exit(1);
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}
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fd = open(argv[1],O_RDONLY);
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if(fd == -1)
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{
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perror("Opening file fails");
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exit(2);
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}
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i = strtol(argv[2],NULL,0);
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offset = i* sizeof(int);
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l = lseek(fd,offset,SEEK_SET);
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if(l == -1)
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{
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perror("lseek fails");
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exit(3);
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}
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n = read(fd,&x,sizeof(int));
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if(n ==-1)
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{
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perror("road in file fails");
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exit(4);
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}
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if(n == 0)
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{
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printf("Offset is out of range!\n");
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}
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else
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{
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printf("The number at offset %d is 0x%08e --> %d\n",i,x,x);
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}
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close(fd);
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exit(0);
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} |