c | compare string format

Question

I want to find out if there is any simple option to a string is equal to a format string. for example I want this format .mat[something][something] to be equal to using strcmp to .mat[r1][r2] or .mat[4][5]

Is there any option to use regular expressions of a sort? or something like strcmp(.mat[%s][%s], .mat[r3][r5])?

BTW I'm using ansi-c Thanks

ansi-c doesn't have support for regular expressions. You can use POSIX regexps if you are on Posix system. — SergeyA, Aug 08 '17 at 15:54

chqrlie · Accepted Answer · 2017-08-08T17:12:36.333

3

Using the closest thing to regular expression, scanf scan sets, this would work, but it is remarkably ugly:

char row[20], col[20], bracket[2], ignored;
if (sscanf(input, ".mat[%19[^]]][%19[^]]%1[]]%c", row, col, bracket, &ignored) == 3) {
    // row and col contain the corresponding specifications...    
    // bracket contains "]"
    // %c failed to convert because if the end of string
    ....
}

Here is the broken down conversion specification for ".mat[r1][r2]":

".mat["    // matches .mat[
"%19[^]]"  // matches r1   count=1
"]["       // matches ][
"%19[^]]"  // matches r2   count=2
"%1[]]"    // matches ]    count=3
"%c"       // should not match anything because of the end of string

edited Aug 08 '17 at 17:12

answered Aug 08 '17 at 16:17

chqrlie

131,814
10
121
189

Maybe `".mat[%19[^]][%19[^]]%1[]]%c"` ( 1 less `]`) – chux - Reinstate Monica Aug 08 '17 at 17:01
1

@chux: Amazingly unreadable isn't it? The third `]` is needed to match the `]` in the string. It is not present for the second part because `%1[]]` matches the second `]` in the string. – chqrlie Aug 08 '17 at 17:09
Agree 3 `]]]` For somewhat improved readability `#define INDEX "%19[^]]" ... ".mat[" INDEX "][" INDEX "%1[]]%c"` – chux - Reinstate Monica Aug 08 '17 at 17:12

score 1 · Answer 2 · answered Aug 08 '17 at 17:30

Alternative to @chqrlie fine answer: This allows for various suffixes and no bracket[2]

Use "%n" which saves the scan offset. It will be non-zero if scanning succeeded up to that point

// .mat[something][something]
#define PREFIX ".mat"
#define IDX "[%19[^]]]"
#define SUFFIX ""

char r1[20], r2[20];
int n = 0;
sscanf(input, PREFIX INDEX INDEX SUFFIX "%n", r1, r2, &n);

// Reached the end and there was no more
if (n > 0 && input[n] == '\0') Success();
else Failure();

c | compare string format

2 Answers2