strncmp

Compare first n characters of strings (case sensitive)

Syntax

tf = strncmp(s1,s2,n)

Description

tf = strncmp(s1,s2,n) compares up to n characters of s1 and s2. The function returns 1 (true) if the two are identical and 0 (false) otherwise. Text is considered identical if the content of each is the same up to the end or the first n characters, whichever comes first. The return result tf is of data type logical.

The first two input arguments can be any combination of string arrays, character vectors, and cell arrays of character vectors.

Examples

Compare First N Characters of Character Vectors

Create two different character vectors. Compare the first 11 characters of them.

s1 = 'Kansas City, KS';
s2 = 'Kansas City, MO';
tf = strncmp(s1,s2,11)

tf = logical
   1

tf is 1 because both character vectors start with 'Kansas City'.

Compare the two character vectors using strcmp.

tf = strcmp(s1,s2)

tf = logical
   0

tf is 0 because s1 and s2 end with different characters.

Find Text That Starts with Same Characters

Starting in R2017a, you can create strings using double quotes. Create a string array that contains names. Find the names that start with 'Jean'.

s1 = ["Jacques";
      "Jean";
      "Jeanne";
      "Jean-Luc";
      "Julie"];
s2 = "Jean";

tf = strncmp(s1,s2,4)

tf = 5x1 logical array

   0
   1
   1
   1
   0

tf is 1 for all names whose first four characters are 'Jean'.

Alternatively, you can use the startsWith function.

tf = startsWith(s1,s2)

tf = 5x1 logical array

   0
   1
   1
   1
   0

Input Arguments

s1,s2 — Input text

character vector | character array | cell array of character vectors | string array

Input text, with each input specified as a character vector, a character array, a cell array of character vectors, or a string array. The order of the inputs does not affect the comparison results.

• If both s1 and s2 are string arrays or cell arrays of character vectors, then s1 and s2 must be the same size, unless one of them is scalar.

• If both s1 and s2 are character arrays with multiple rows, then s1 and s2 can have different numbers of rows.

• When comparing a nonscalar cell array of character vectors or string array to a multirow character array, the cell array or string array must be a column vector with the same number of rows as the character array.

Data Types: char | cell | string

n — Maximum number of characters to compare

integer

Maximum number of characters to compare, specified as an integer.

• If n is 0, then strncmp always returns 1. By convention, the zeroth character of a character vector or a string scalar is always '', a 0-by-0 character array.

• If n is less than 0, then strncmp treats it as 0.

Data Types: double | single | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Output Arguments

tf — True or false result

1 | 0 | logical array

True or false result, returned as a 1 or 0 of data type logical.

• If each input is either a string scalar or a character vector, then tf is a scalar.

• If at least one input is either a string array or a cell array of character vectors, then tf is an array the same size as the input array.

• If one input is a character array with multiple rows, and the other input is either a scalar cell or a string scalar, then tf is an n-by-1 array, where n is the number of rows in the character array.

• If both inputs are character arrays, then tf is a scalar.

Tips

• The strncmp function is intended for comparison of text. If used on numeric arrays, strncmp always returns 0.

• For case-insensitive text comparison, use strncmpi instead of strncmp.

• Although strncmp shares a name with a C function, it does not follow the C language convention of returning 0 when the text inputs match.

Extended Capabilities

Tall Arrays

Calculate with arrays that have more rows than fit in memory.

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

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• Enumeration inputs are not supported.

• When one input is a cell array and the other input is a character array, the character array must be a compile-time row vector.

Distributed Arrays

Partition large arrays across the combined memory of your cluster using Parallel Computing Toolbox™.

Usage notes and limitations:

• s1 and s2 must be string arrays or cell arrays of character vectors.

For more information, see Run MATLAB Functions with Distributed Arrays (Parallel Computing Toolbox).