使用c从文件读取特定范围的行

Question

I have the following content in a file:

hhasfghgsafjgfhgfhjf
gashghfdgdfhgfhjasgfgfhsgfjdg
jfshafghgfgfhfsghfgffsjgfj
.
.
.
.
.
startread
hajshjsfhajfhjkashfjf
hasjgfhgHGASFHGSHF
hsafghfsaghgf
.
.
.
.
.
stopread
.
.
.
.
.
.
jsfjhfhjgfsjhfgjhsajhdsa
jhasjhsdabjhsagshaasgjasdhjk
jkdsdsahghjdashjsfahjfsd

I need to read the lines from the next line of startread till the previous line of stopread using ac code and store it to a string variable(of course with a \\n for every line breaks). How can i achieve this? I have used fgets(line,sizeof(line),file); but it starts reading from the beginning. I don't have the exact line number to start and stop reading since the file is written by another C code. But there are these identifiers startread and stopread to identify whereto start reading. Operating platform is linux. Thanks in advance.

Answer 1

Use strcmp() to detect startread and stopread . Ignore all lines read until "startread" is read and then store all lines until "stopread" is read:

/* Read until "startread". */
char line[1024];
while (fgets(line, sizeof(line), file) &&
       0 != strcmp(line, "startread\n"));

/* Read until "stopread", only if "startread" found. */
if (0 == strcmp(line, "startread\n"))
{
    while (fgets(line, sizeof(line), file) &&
           0 != strcmp(line, "stopread\n"))
    {
        /* Do something with 'line'. */
    }
}

Answer 2

    #define MAX_BUF_LEN 1000    
    int flag=0;
    while(fgets(buf, MAX_BUF_LEN, file) != NULL){
       if(strncmp(buf, "startread", strlen("startread")) == 0){
          flag=1;
       }
       else if (strncmp(buf, "stopread", strlen("stopread")) == 0){
          flag=0;
       }

       if(flag){
          strncpy(line, buf, strlen(buf));
         // strncat(line, '\n', strlen('\n'));
       }

    // that's all!
    }
    fclose(file);

This should works.