I wanna know why sscanf is storing the \n in the date buffer, how can I avoid it in order to have an output like this? : YYYY_MM_DD1234
char yyyy[10];
char mm[10];
char dd[10];
char date[100];
puts("Give the date YYYY/MM/DD");
fgets(date, sizeof date, stdin);
sscanf(date, "%10[^_]_%10[^_]_%10[^_]", yyyy, mm, dd);
strcat(date, "1234");
printf("%c", date);
This is the output given by the program:
Output : YYYY_MM_DD
1234
If I understand what you are trying to do, take "YYYY/MM/DD" and rearrange it to "YYYY_MM_DD1234", then continuing from my comment, all you need is to separate your input with sscanf and create a new string with sprintf.
All line-oriented input functions (fgets() and POSIX getline()) read and include the '\n' in the buffer they fill. Your %10[^_] includes the '\n' following DD input in dd. You will need to change your sscanf format string to:
sscanf (date, " %9[^/]/%9[^/]/%9[^\n]", yyyy, mm, dd)
Then you simply write to a new string with:
sprintf (newfmt, "%s_%s_%s1234", yyyy, mm, dd);
A short example would be:
#include <stdio.h>
#define NCHR 10 /* if you need a constant, #define one (or more) */
int main (void) {
char yyyy[NCHR],
mm[NCHR],
dd[NCHR],
date[NCHR*NCHR],
newfmt[NCHR*NCHR];
fputs ("Give the date YYYY/MM/DD: ", stdout);
if (fgets (date, sizeof date, stdin)) {
if (sscanf (date, " %9[^/]/%9[^/]/%9[^\n]", yyyy, mm, dd) != 3) {
fputs ("error: invalid date format.\n", stderr);
return 1;
}
sprintf (newfmt, "%s_%s_%s1234", yyyy, mm, dd);
puts (newfmt);
}
}
Example Use/Output
$ ./bin/newdatefmt
Give the date YYYY/MM/DD: YYYY/MM/DD
YYYY_MM_DD1234
Look things over and let me know if you have any further questions.
First of all, you need to know that %10[^_] reads 10 characters or everything until a _ character, whichever comes first.
Now, back to your code, fgets(date, sizeof date, stdin); reads in YYYY_MM_DD\n from the user.
Now lets break "%10[^_]_%10[^_]_%10[^_]" down:
%10[^_] reads YYYY (and stops as the next character is a _) and stores it in yyyy_ reads and discards the _%10[^_] reads MM (and stops as the next character is a _) and stores it in mm_ reads and discards the _%10[^_] reads DD\n (and stops as it reached the end of the string) and stores it in ddSee the problem?
A simple fix would be to change the final %10[^_] to %10[^\n] so that it scans everything until a newline character as opposed to everthing until a _ character.
Side note: You should be using 9 instead of 10 in the sscanf string as you'd need to reserve one space for the NUL-terminator (\0) marking the end of the string. Also, as @chux says in a comment, it is recommended to check the return value of sscanf to make sure that everything has been parsed successfully. It returns the number of items successfully scanned and assigned. In your case, it it returns 3, we're good to go!
The following proposed code:
and now, the proposed code:
#include <stdio.h>
#include <string.h>
int main( void )
{
char date[100];
puts("Give the date YYYY/MM/DD");
// -5 to allow room for "1234" which will be added later
fgets(date, sizeof(date) -5, stdin);
// remove posssible trailing newline
date[ strcspn( date, "\n" ) ] = '\0';
//convert each '/' to '_'
for( size_t i=0; date[i]; i++ )
{
if( date[i] == '/' )
{
date[i] = '_';
}
}
// append the desired trailing string
strcat(date, "1234");
// display the resulting string on the terminal
printf("%s\n", date);
}
This code below is to get a string with scanf. You don't have to use fgets() for the code above. fgets() is actually the one that consumes the end line character. Since you probably don't want to go through that string to remove that end line from fgets(). You can directly use scanf and this method below is not that unsafe either. I provide the tester below so you can test it out. Don't use fflush(stdin), that does not always work.
This is the string to look at. Also, thank you to @JonathanLeffler and @chux-ReinstateMonica for pointing it out that I don't the s after %*[^\n].
"%10s%*[^\n]"
It just meant read up to 10 characters into a string. If the user input more than 10 characters then everything else after 10 will be discarded but not the end line. Then right after that, use a blank getchar() to remove that end line.
Also, you used fget() for date and not sscanf. So your problem is not a sscanf problem. sscanf will not store the end line into your buffer. Also, I removed the test code and just left behind your code with a fix. From the old code, I even left fflush(stdin) in there. I was just testing to see if it was working across compilers :). Also, remember your string format needed 10 characters, so your buffer or array should be of length 11.
Although that, remember that data validation is your issue, you did not ask how to validate the date array.
#include <stdio.h>
#include <string.h>
int main()
{
char yyyy[10];
char mm[10];
char dd[10];
char date[100];
puts("Give the date YYYY/MM/DD");
// Discard everything except endl
scanf("%10s%*[^\n]", date);
// Get endl out of stdin
getchar();
sscanf(date, "%4s%*c%2s%*c%2s", yyyy, mm, dd);
strcat(date, "1234");
printf("Date: %s\n", date);
}
