# Documentation

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# strncmp

Compare first n characters of strings (case sensitive)

## Syntax

TF = strncmp(str,str,n)
TF = strncmp(str,C,n)
TF = strncmp(C,C,n)

## Description

TF = strncmp(str,str,n) compares the first n characters of two character vectors for equality. The function returns a scalar logical 1 for equality, or scalar logical 0 for inequality.

TF = strncmp(str,C,n) compares the first n characters of a character vector with the first n characters of each element of a cell array of character vectors. The function returns a logical array the same size as the C input in which logical 1 represents equality. The order of the first two input arguments is not important.

TF = strncmp(C,C,n) compares each element of one cell array of character vectors with the same element of the other. strncmp attempts to match only the first n characters of these character vectors. The function returns a logical array the same size as either input array.

## Input Arguments

 str A character vector or m-by-n character array. C Cell array of character vectors. n Maximum number of characters to compare. Must be a scalar, integer-valued double.

## Output Arguments

 TF When both inputs are character arrays, TF is a scalar logical value. This value is logical 1 (true) if the size and content of both arrays are equal, and logical 0 (false) if they are not. When either or both inputs are a cell array of character vectors, TF is an array of logical ones and zeros. This array is the same size as the input cell array(s), and contains logical 1 (true) for those elements of the input arrays that are a match, and logical 0 (false) for those elements that are not.

## Examples

Before trying the strncmp function, use strcmp to perform a simple comparison of the two input character vectors. Because only the first 13 characters are the same, strcmp returns logical 0:

strcmp('Kansas City, KS', 'Kansas City, MO')
ans =
0

Do the comparison again, but this time using strncmp and specifying the number of characters to compare:

chars2compare = length('Kansas City, KS') - 2
ans =
13
strncmp('Kansas City, KS', 'Kansas City, MO', chars2compare)
ans =
1

From a list of 10 MATLAB® functions, find those that apply to using a camera:

function_list = {'calendar' 'case' 'camdolly' 'circshift' ...
'caxis' 'camtarget' 'cast' 'camorbit' ...
'callib' 'cart2sph'};

strncmp(function_list, 'cam', 3)
ans =
0    0    1    0    0    1    0    1    0    0

function_list{strncmp(function_list, 'cam', 3)}
ans =
camdolly
ans =
camtarget
ans =
camorbit

Create two 5-by-10 character arrays str1 and str2 that are equal, except for the element at row 4, column 3. Using linear indexing, this is element 14:

str1 = ['AAAAAAAAAA'; 'BBBBBBBBBB'; 'CCCCCCCCCC'; ...
'DDDDDDDDDD'; 'EEEEEEEEEE']
str1 =
AAAAAAAAAA
BBBBBBBBBB
CCCCCCCCCC
DDDDDDDDDD
EEEEEEEEEE

str2 = str1;
str2(4,3) = '-'
str2 =
AAAAAAAAAA
BBBBBBBBBB
CCCCCCCCCC
DD-DDDDDDD
EEEEEEEEEE

Because MATLAB compares the arrays in linear order (that is, column by column rather than row by row), strncmp finds only the first 13 elements to be the same:

str1   A B C D E A B C D E A B C D E
str2   A B C D E A B C D E A B C - E
|
element 14

strncmp(str1, str2, 13)
ans =
1

strncmp(str1, str2, 14)
ans =
0

collapse all

### Tall Array Support

This function fully supports tall arrays. For more information, see Tall Arrays.

### Tips

• The strncmp function is intended for comparison of character data. When used to compare numeric data, it returns logical 0.

• Use strncmpi for case-insensitive text comparisons.

• Any leading and trailing blanks in either of the character vectors are explicitly included in the comparison.

• The value returned by strncmp is not the same as the C language convention.

• strncmp supports international character sets.