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  • C language——to Replace a specified Line in a Text File—V2

    [root@localhost 桌面]# gedit tmp.c

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    1. // C Language to Replace a specified Line in a Text File

    3. #include <stdio.h>
    4. #include <stdlib.h>
    5. #include <string.h>

    7. //filename: "/etc/hosts"
    8. //str: "mpe.localhost"
    9. //return the matched line number
    10. int findline(char *filename, char *str)
    11. {
    12.     // open the file for reading
    13.     FILE *file = fopen(filename, "r");

    15.     // make sure the file opened properly
    16.     if(NULL == file)
    17.     {
    18.         fprintf(stderr, "Cannot open file: %s ", filename);
    19.         return 1;
    20.     }

    22.     // set up the buffer to read the line into. Don't worry too much
    23.     // if some of the lines are longer than 80 characters - the buffer
    24.     // will be made bigger if need be.
    25.     size_t buffer_size = 80;
    26.     char *buffer = malloc(buffer_size * sizeof(char));

    28.     // read each line and print it to the screen
    29.     int line_number = 0, find = 0;
    30.     while(-1 != getline(&buffer, &buffer_size, file))
    31.     {
    32.         line_number++;
    33.         if(NULL != strstr(buffer, str))
    34.         {
    35.             find = 1;
    36.             break;
    37.         }
    38.         //printf("%d: %s", line_number, buffer);
    39.     }

    41.     if(find == 0) line_number = 0;

    43.     fclose(file);
    44.     free(buffer);

    46.     return line_number;
    47. }

    49. void replaceline(char *filename, int delete_line, char *newcontent)
    50. {
    51.     FILE *fileptr1, *fileptr2;
    52.     //char filename[40];
    53.     char c;
    54.     int temp = 1;

    56.     fileptr1 = fopen(filename, "r");
    57.     //print the contents of file .
    58.     while ((c = getc(fileptr1)) != EOF)
    59.     {
    60.         printf("%c", c);
    61.     }

    63.     //take fileptr1 to start point.
    64.     rewind(fileptr1);
    65.     //open tempinterm.txt in write mode
    66.     fileptr2 = fopen("tempinterm.txt", "w");

    68.     while ((c = getc(fileptr1)) != EOF)
    69.     {
    70.         //till the line to be deleted comes,copy the content to other
    71.         if (temp != delete_line) {
    72.             putc(c, fileptr2);
    73.             while ((c = getc(fileptr1)) != 'n') putc(c, fileptr2);
    74.             putc('n', fileptr2);
    75.             temp++;
    76.         } else {
    77.             while ((c = getc(fileptr1)) != 'n');    //read and skip the line
    78.             //while ((c = getchar()) != 'n') putc(c, fileptr2);
    79.             while(*newcontent != '0') putc(*newcontent++, fileptr2);
    80.             putc('n', fileptr2);
    81.             temp++;
    82.         }
    83.     }

    85.     //append a new line at the end of file
    86.     if(delete_line == 0)
    87.     {
    88.         while(*newcontent != '0') putc(*newcontent++, fileptr2);
    89.         putc('n', fileptr2);
    90.     }

    92.     fclose(fileptr1);
    93.     fclose(fileptr2);
    94.     remove(filename);
    95.     rename("tempinterm.txt", filename);
    96. }

    98. int main(void)
    99. {
    100.     FILE *fileptr1;
    101.     char c;

    103.     char filename[6] = "hosts";

    105.     int line = findline(filename, "mpe.localhost");
    106.     replaceline(filename, line, "10.108.162.227 mpe.localhost");

    108.     fileptr1 = fopen(filename, "r");
    109.     //reads the character from file
    110.     //until last character of file is encountered
    111.     while ((c = getc(fileptr1)) != EOF) printf("%c", c);
    112.     fclose(fileptr1);
    113.     return 0;
    114. }
    [root@localhost 桌面]# gcc tmp.c -o tmp
    [root@localhost 桌面]# ./tmp
    127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
    ::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
    127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
    ::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
    10.108.162.227   mpe.localhost
    [root@localhost 桌面]#





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  • 原文地址：https://www.cnblogs.com/ztguang/p/12649502.html
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