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### 5.4 Comparing Strings

Since a string is a character array, comparisons between strings work element by element as the following example shows:

         GNU = "GNU's Not UNIX";
         spaces = (GNU == " ")
               spaces =
                0   0   0   0   0   1   0   0   0   1   0   0   0   0

To determine if two strings are identical it is necessary to use the `strcmp` function. It compares complete strings and is case sensitive. `strncmp` compares only the first `N` characters (with `N` given as a parameter). `strcmpi` and `strncmpi` are the corresponding functions for case-insensitive comparison.

— Built-in Function: strcmp (s1, s2)

> Return 1 if the character strings s1 and s2 are the same, and 0 otherwise.

> If either s1 or s2 is a cell array of strings, then an array of the same size is returned, containing the values described above for every member of the cell array. The other argument may also be a cell array of strings (of the same size or with only one element), char matrix or character string.

> Caution: For compatibility with matlab, Octave's strcmp function returns 1 if the character strings are equal, and 0 otherwise. This is just the opposite of the corresponding C library function.

> See also: strcmpi, strncmp, strncmpi.

— Built-in Function: strncmp (s1, s2, n)

> Return 1 if the first n characters of strings s1 and s2 are the same, and 0 otherwise.

>               strncmp ("abce", "abcd", 3)
>                     1

> If either s1 or s2 is a cell array of strings, then an array of the same size is returned, containing the values described above for every member of the cell array. The other argument may also be a cell array of strings (of the same size or with only one element), char matrix or character string.

>               strncmp ("abce", {"abcd", "bca", "abc"}, 3)
>                     [1, 0, 1]

> Caution: For compatibility with matlab, Octave's strncmp function returns 1 if the character strings are equal, and 0 otherwise. This is just the opposite of the corresponding C library function.

> See also: strncmpi, strcmp, strcmpi.

— Function File: strcmpi (s1, s2)

> Ignoring case, return 1 if the character strings (or character arrays) s1 and s2 are the same, and 0 otherwise.

> If either s1 or s2 is a cell array of strings, then an array of the same size is returned, containing the values described above for every member of the cell array. The other argument may also be a cell array of strings (of the same size or with only one element), char matrix or character string.

> Caution: For compatibility with matlab, Octave's strcmpi function returns 1 if the character strings are equal, and 0 otherwise. This is just the opposite of the corresponding C library function.

> See also: strcmp, strncmp, strncmpi.

— Function File: strncmpi (s1, s2, n)

> Ignoring case, return 1 if the first n characters of character strings (or character arrays) s1 and s2 are the same, and 0 otherwise.

> If either s1 or s2 is a cell array of strings, then an array of the same size is returned, containing the values described above for every member of the cell array. The other argument may also be a cell array of strings (of the same size or with only one element), char matrix or character string.

> Caution: For compatibility with matlab, Octave's strncmpi function returns 1 if the character strings are equal, and 0 otherwise. This is just the opposite of the corresponding C library function.

> See also: strcmp, strcmpi, strncmp.

— Function File: validstr = validatestring (str, strarray)
— Function File: validstr = validatestring (str, strarray, funcname)
— Function File: validstr = validatestring (str, strarray, funcname, varname)
— Function File: validstr = validatestring (..., position)

> Verify that str is a string or substring of an element of strarray.

> str is a character string to be tested, and strarray is a cellstr of valid values. validstr will be the validated form of str where validation is defined as str being a member or substring of validstr. If str is a substring of validstr and there are multiple matches, the shortest match will be returned if all matches are substrings of each other, and an error will be raised if the matches are not substrings of each other.

> All comparisons are case insensitive.

> See also: strcmp, strcmpi.