61 lines
1.8 KiB
C
61 lines
1.8 KiB
C
/*********************************************************************************************
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Description: Get specific line of a txt file
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Copyright : All right reserved by NCIC.ICT
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Author : Zhang Zhonghai
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Date : 2023/08/28
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***********************************************************************************************/
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#define READ_BUF_SIZE 102400000
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int main(int argc, char *argv[])
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{
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if (argc < 3)
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{
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fprintf(stderr, "Please input the file path and the line number you want to get!\n");
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return 1;
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}
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const char *in_path = argv[1];
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size_t expect_line_num = atoi(argv[2]);
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FILE *in_f = fopen(in_path, "r");
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char *read_buf = (char *)malloc(READ_BUF_SIZE);
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int actual_size = 0;
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int expect_size = READ_BUF_SIZE;
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size_t cur_line_num = 0;
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size_t last_line_pos = 0;
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size_t cur_line_pos = 0;
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int i, j;
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int flag_found = 0;
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// 读取数据
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actual_size = fread(read_buf, 1, expect_size, in_f);
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while (actual_size > 0)
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{
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for (i = 0; i < actual_size; ++i)
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if (read_buf[i] == '\n')
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{
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cur_line_num += 1;
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last_line_pos = cur_line_pos;
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cur_line_pos = i;
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if (cur_line_num == expect_line_num)
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{
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for (j = last_line_pos + 1; j <= cur_line_pos; ++j)
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{
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fprintf(stdout, "%c", read_buf[j]);
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}
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flag_found = 1;
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break;
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}
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}
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if (flag_found)
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break;
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actual_size = fread(read_buf, 1, expect_size, in_f);
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}
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if (!flag_found)
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fprintf(stderr, "Invalid line number!\n");
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return 0;
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} |