String Functions

Function File: strcmp (s1, s2)

Compares two strings, returning 1 if they are the same, and 0 otherwise.

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

Function File: int2str (n)

Function File: num2str (x)

Convert a number to a string. These functions are not very flexible, but are provided for compatibility with MATLAB. For better control over the results, use sprintf (see section Formatted Output).

Built-in Function: setstr (x)

Convert a matrix to a string. Each element of the matrix is converted to the corresponding ASCII character. For example,

setstr ([97, 98, 99])

creates the string

abc

Built-in Variable: implicit_str_to_num_ok

If the value of implicit_str_to_num_ok is nonzero, implicit conversions of strings to their numeric ASCII equivalents are allowed. Otherwise, an error message is printed and control is returned to the top level. The default value is 0.

Built-in Function: undo_string_escapes (s)

Converts special characters in strings back to their escaped forms. For example, the expression

bell = "\a";

assigns the value of the alert character (control-g, ASCII code 7) to the string variable bell. If this string is printed, the system will ring the terminal bell (if it is possible). This is normally the desired outcome. However, sometimes it is useful to be able to print the original representation of the string, with the special characters replaced by their escape sequences. For example,

octave:13> undo_string_escapes (bell)
ans = \a

replaces the unprintable alert character with its printable representation. See section String Constants, for a description of string escapes.

Function File: bin2dec (s)

Given a binary number represented as a string of zeros and ones, returns the corresponding decimal number. For example,

bin2dec ("1110")
    => 14

Function File: blanks (var{n})

Returns a string of n blanks.

Function File: deblank (s)

Removes the trailing blanks from the string s.

Function File: dec2bin (n)

Given a nonnegative integer, returns the corresponding binary number as a string of ones and zeros. For example,

dec2bin (14)
  => "1110"

Function File: dec2hex (n)

Given a nonnegative integer, returns the corresponding hexadecimal number as a string. For example,

dec2hex (2748)
   => "abc"

Function File: findstr (s, t, overlap)

Returns the vector of all positions in the longer of the two strings s and t where an occurence of the shorter of the two starts. If the optional argument overlap is nonzero, the returned vector can include overlapping positions (this is the default). For example,

findstr ("ababab", "a")
   => [1  3  5]
findstr ("abababa", "aba", 0)
   => [1, 5]

Function File: hex2dec (s)

Given a hexadecimal number represented as a string, returns the corresponding decimal number. For example,

hex2dec ("12B")
   => 299
hex2dec ("12b")
   => 299

Function File: index (s, t)

Returns the position of the first occurence of the string t in the string s, or 0 if no occurence is found. For example,

index ("Teststring", "t")
   => 4

Note: This function does not work for arrays of strings.

Function File: rindex (s, t)

Returns the position of the last occurence of the string t in the string s, or 0 if no occurence is found. For example,

rindex ("Teststring", "t")
   => 6

Note: This function does not work for arrays of strings.

Function File: split (s, t)

Divides the string s into pieces separated by t, returning the result in a string array (padded with blanks to form a valid matrix). For example,

split ("Test string", "t")
   => Tes 
       s  
      ring

Function File: str2num (s)

Convert the string s to a number.

Function File: str2mat (s_1, ..., s_n)

Returns a matrix containing the strings s_1, ..., s_n as its rows. Each string is padded with blanks in order to form a valid matrix.

Note: This function is modelled after MATLAB. In Octave, you can create a matrix of strings by [s_1; ...; s_n].

Built-in Variable: string_fill_char

Function File: strrep (s, x, y)

Replaces all occurences of the substring x of the string s with the string y. For example,

strrep ("This is a test string", "is", "&%$")
   => Th&%$ &%$ a test string

Function File: substr (s, beg, len)

Returns the substring of s which starts at character number beg and is len characters long. For example,

substr ("This is a test string", 6, 9)
   => is a test

Note: This function is patterned after AWK. You can get the same result by s (beg : (beg + len - 1)).

Function File: tolower (s)

Return a copy of the string s, with each upper-case character replaced by the corresponding lower-case one; nonalphabetic characters are left unchanged. For example,

tolower ("MiXeD cAsE 123")
   => "mixed case 123"

Function File: toupper (s)

Returns a copy of the string s, with each lower-case character replaced by the corresponding upper-case one; nonalphabetic characters are left unchanged. For example,

toupper ("MiXeD cAsE 123")
   => "MIXED CASE 123"

Function File: toascii (s)

Return ASCII representation of s in a matrix. For example,

toascii ("ASCII")
   => [ 65, 83, 67, 73, 73 ]

Octave also provides the following C-type character class test functions. They all operate on string arrays and return matrices of zeros and ones. Elements that are nonzero indicate that the condition was true for the corresponding character in the string array.

Mapping Function: isalnum (s)

letter or a digit

Mapping Function: isalpha (s)

letter

Mapping Function: isascii (s)

ascii

Mapping Function: iscntrl (s)

control character

Mapping Function: isdigit (s)

digit

Mapping Function: isgraph (s)

printable (but not space character)

Mapping Function: islower (s)

lower case

Mapping Function: isprint (s)

printable (including space character)

Mapping Function: ispunct (s)

punctuation

Mapping Function: isspace (s)

whitespace

Mapping Function: isupper (s)

upper case

Mapping Function: isxdigit (s)

hexadecimal digit

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