| ISCNTRL(3) | Library Functions Manual | ISCNTRL(3) | 
iscntrl —
control character test
Standard C Library (libc, -lc)
#include <ctype.h>
int
  
  iscntrl(int
    c);
The iscntrl() function tests for any control character.
The iscntrl() function returns zero if the character
  tests false and returns non-zero if the character tests true.
ctype(3),
  isalnum(3),
  isalpha(3),
  isascii(3),
  isblank(3),
  isdigit(3),
  isgraph(3),
  islower(3),
  isprint(3),
  ispunct(3),
  isspace(3),
  isupper(3),
  isxdigit(3),
  stdio(3),
  toascii(3),
  tolower(3),
  toupper(3),
  ascii(7)
The iscntrl() function conforms to ANSI
  X3.159-1989 (“ANSI C89”).
The argument to iscntrl() must be
  EOF or representable as an unsigned
  char; otherwise, the behavior is undefined. See the
  CAVEATS section of
  ctype(3) for more details.