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ISCNTRL(3) FreeBSD Library Functions Manual ISCNTRL(3) NAME iscntrl, iscntrl_l - control character test LIBRARY Standard C Library (libc, -lc) SYNOPSIS #include <ctype.h> int iscntrl(int c); int iscntrl_l(int c, locale_t loc); DESCRIPTION The iscntrl() and iscntrl_l() functions test for any control character. The value of the argument must be representable as an unsigned char or the value of EOF. In the ASCII character set, this includes the following characters (with their numeric values shown in octal): 000 NUL 001 SOH 002 STX 003 ETX 004 EOT 005 ENQ 006 ACK 007 BEL 010 BS 011 HT 012 NL 013 VT 014 NP 015 CR 016 SO 017 SI 020 DLE 021 DC1 022 DC2 023 DC3 024 DC4 025 NAK 026 SYN 027 ETB 030 CAN 031 EM 032 SUB 033 ESC 034 FS 035 GS 036 RS 037 US 177 DEL The iscntrl_l() function takes an explicit locale argument, whereas the iscntrl() function uses the current global or per-thread locale. RETURN VALUES The iscntrl() and iscntrl_l() functions return zero if the character tests false and return non-zero if the character tests true. COMPATIBILITY The 4.4BSD extension of accepting arguments outside of the range of the unsigned char type in locales with large character sets is considered obsolete and may not be supported in future releases. The iswcntrl() or iswcntrl_l() function should be used instead. SEE ALSO ctype(3), ctype_l(3), iswcntrl(3), iswcntrl_l(3), xlocale(3), ascii(7) STANDARDS The iscntrl() function conforms to ISO/IEC 9899:1990 ("ISO C90"). The iscntrl_l() function conforms to IEEE Std 1003.1-2008 ("POSIX.1"). HISTORY The iscntrl() function first appeared in Version 7 AT&T UNIX. FreeBSD 14.1-RELEASE-p8 December 19, 2022 FreeBSD 14.1-RELEASE-p8