Reading data separated by ';' from file

Question

I am trying to read in data from a file that is formatted with ;. The data will always be of like this:

char[];int;int%;int

The char[] can have any number of spaces and the % should be disregarded when reading the data.

I am using fscanf() (I am allowed to use only that) for reading the data from the file.
Right now my code for that part of it is:

fscanf(file, "%[^;]%d%d%d", f_name, &f_id, &f_score, &f_section_num) != EOF)

Is there a regex for what I need? Or, how do I correct my fscanf?

See if this helps. https://stackoverflow.com/questions/19466894/how-to-read-through-data-in-a-file-and-pass-it-to-a-struct-c/19467418#19467418 — Anand, Sep 07 '18 at 20:55
what about something like`while(4 == fscanf(file, "%[^;];%d;%d%%;%d", ...));` — Mathieu, Sep 07 '18 at 20:56
@Anand I looked at that before posting this question and even tried what they did, but I am still getting an error. — MinorMapillai, Sep 07 '18 at 21:04
note that due to `%[^;]`, which also consumes a new line character, your program will read in a two-line input like `abc\nxyz;3;4%;5` as one line. — Stephan Lechner, Sep 07 '18 at 21:22
`fscan` does not support regex. For the syntax of the format string, what abou the documentation is unclear? — too honest for this site, Sep 07 '18 at 22:02

Mathieu · Accepted Answer · 2018-09-07T21:16:41.947

You can read the file using fscanf with this format string:

"%[^;];%d;%d%%;%d"

%[^;]: read up to first ;
;: ignore the ;
%d: read one integer
;: ignore the ;
%d: read one second integer
%%: ignore the %
;: ignore the ;
%d: read one third integer

Do not forget to test the number of successful conversions made by fscanf by testing fscanf(...) == 4

So code will looks like:

FILE *f = fopen(...);
char name[64];
int i, integers[3];

while (fscanf(f, "%[^;];%d;%d%%;%d", name, &integers[0], &integers[1], &integers[2]) == 4)
{
    printf("name is %s\n", name);
    for (i = 0; i < 3; ++i)
    {
        printf("i[%d] = %d\n", i, integers[i]);
    }        
}
fclose(f);

score 0 · Answer 2 · edited Sep 08 '18 at 00:27

0

The following code will allow you to read data separated by ; from your file:

char msg[100];
int  a;
char b[100];
int  c;

fscanf(fptr, "%[^;];%d;%[^;];%d", msg, &a, b, &c);
printf("%s\n %d\n %d\n %d\n", msg, a, atoi(b), c);

edited Sep 08 '18 at 00:27

Grant Miller

27,532
16
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165

answered Sep 07 '18 at 21:11

Anand

374
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This assumes, perhaps unsafely, that no component on the line will exceed 99 characters. – tadman Sep 07 '18 at 21:24
1

The third field is, I think, meant to be an integer followed by `%`, so `;25%;` or similar. You seem to be treating it as a string, which is only partially correct — you'd have to convert the string to an integer, possibly after validating for a percent symbol at the end. – Jonathan Leffler Sep 07 '18 at 22:00

David Collins · Answer 3 · 2018-09-07T21:53:43.633

You could, alternatively, use strtok(). If, for example, you use a struct for each entry as follows,

typedef struct {
    char name[64];
    int id, score, section_num;
} entry_t;

the following would read each line of the file as follows.

char line[128] = {'\0'};
char *field = NULL;
entry_t entry;

while (fgets(line, sizeof(line), fp)) {
    field = strtok(line, ";");
    if (!field || strlen(field) > sizeof(entry.name)) continue;
    strcpy(entry.name, field);
    field = strtok(NULL, ";");
    if (!field) continue;
    entry.id = atoi(field);
    field = strtok(NULL, ";%");
    if (!field) continue;
    entry.score = atoi(field);
    field = strtok(NULL, ";");
    if (!field) continue;
    entry.section_num = atoi(field);
    // Do whatever you need with the entry - e.g. print its contents
}

I have removed some necessary boilerplate code for brevity. See http://codepad.org/lg6BJ0hk for a full example.

You can use strtol() instead of atoi() if you need to check the results of the integer conversions.

I tried using this, but I felt it's a bit unnecessary for what I am doing right now. — MinorMapillai, Sep 07 '18 at 21:51
@Varun.R: It is, admittedly, more long-winded. If you have a solution using `fscanf()`, just go with that I suggest. I think I will leave this answer here anyway, as an alternative. — David Collins, Sep 07 '18 at 21:55

Reading data separated by ';' from file

3 Answers3