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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.

__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.

__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.

__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.`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.

__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.

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