isprint

isprint

Ascertains whether a given character is printable

 #include <ctype.h> int isprint ( int c  );

The isprint( ) function tests whether its argument is a printing character. If the argument is a printing character, isprint( ) returns a nonzero value (that is, TRue); if not, the function returns 0 (false).

"Printing" means only that the character occupies printing space on the output medium, not that it fills the space with a glyph. Thus the space is a printing character (isprint(' ') returns true), even though it does not leave a mark (isgraph(' ') returns false).

Which character codes represent printable characters depends on the current locale setting for the category LC_CTYPE, which you can query or change using the setlocale( ) function. In the default locale C, the printable characters are the alphanumeric characters, the punctuation characters, and the space character; the corresponding character codes are those from 32 through 126.

Example

 unsigned int c; printf("\nThe current locale for the 'is ...' functions is '%s'.\n",        setlocale(LC_CTYPE, NULL)); printf("Here is a table of the 'is ...' values for the characters"        " from 0 to 127 in this locale:\n\n"); for ( c = 0; c < 128; c++ ) // Loop iteration for each table row. {   if ( c % 24 == 0 )        // Repeat table header every 24 rows.   {     printf("Code char alnum alpha blank cntrl digit graph lower"            " print punct space upper xdigit\n");     printf("---------------------------------------------------"            "-------------------------------\n");   }   printf(  "%4u %4c %3c %5c %5c %5c %5c %5c %5c %5c %5c %5c %5c %5c\n",            c,                              // Print numeric character code.            ( isprint( c )  ?  c  : ' ' ),  // Print the glyph, or a space                                            // if it's not printable.            ( isalnum( c )  ? 'X' : '-' ),  // In a column for each category,            ( isalpha( c )  ? 'X' : '-' ),  // print X for yes or - for no.            ( isblank( c )  ? 'X' : '-' ),            ( iscntrl( c )  ? 'X' : '-' ),            ( isdigit( c )  ? 'X' : '-' ),            ( isgraph( c )  ? 'X' : '-' ),            ( islower( c )  ? 'X' : '-' ),            ( isprint( c )  ? 'X' : '-' ),            ( ispunct( c )  ? 'X' : '-' ),            ( isspace( c )  ? 'X' : '-' ),            ( isupper( c )  ? 'X' : '-' ),            ( isxdigit( c ) ? 'X' : '-' ) ); }  // end of loop for each character value

The following selected lines from the table produced by this program include at least one member and one nonmember of each category:

 Code char alnum alpha blank cntrl digit graph lower print punct space upper xdigit ----------------------------------------------------------------------------------   31        -     -     -     X     -     -     -     -     -     -     -     -   32        -     -     X     -     -     -     -     X     -     X     -     -   33    !   -     -     -     -     -     X     -     X     X     -     -     -   48    0   X     -     -     -     X     X     -     X     -     -     -     X   65    A   X     X     -     -     -     X     -     X     -     -     X     X  122    z   X     X     -     -     -     X     X     X     -     -     -     -

Example

See Also