stdio/getc.3

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  36 .\"     @(#)getc.3      8.1 (Berkeley) 6/4/93
  37 .\" $FreeBSD: src/lib/libc/stdio/getc.3,v 1.19 2004/03/17 12:37:28 tjr Exp $
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  39 .Dd January 10, 2003
  40 .Dt GETC 3
  41 .Os
  42 .Sh NAME
  43 .Nm fgetc ,
  44 .Nm getc ,
  45 .Nm getc_unlocked ,
  46 .Nm getchar ,
  47 .Nm getchar_unlocked ,
  48 .Nm getw
  49 .Nd get next character or word from input stream
  50 .Sh LIBRARY
  51 .Lb libc
  52 .Sh SYNOPSIS
  53 .In stdio.h
  54 .Ft int
  55 .Fn fgetc "FILE *stream"
  56 .Ft int
  57 .Fn getc "FILE *stream"
  58 .Ft int
  59 .Fn getc_unlocked "FILE *stream"
  60 .Ft int
  61 .Fn getchar "void"
  62 .Ft int
  63 .Fn getchar_unlocked "void"
  64 .Ft int
  65 .Fn getw "FILE *stream"
  66 .Sh DESCRIPTION
  67 The
  68 .Fn fgetc
  69 function
  70 obtains the next input character (if present) from the stream pointed at by
  71 .Fa stream ,
  72 or the next character pushed back on the stream via
  73 .Xr ungetc 3 .
  74 .Pp
  75 The
  76 .Fn getc
  77 function
  78 acts essentially identically to
  79 .Fn fgetc ,
  80 but is a macro that expands in-line.
  81 .Pp
  82 The
  83 .Fn getchar
  84 function
  85 is equivalent to
  86 .Fn getc stdin .
  87 .Pp
  88 The
  89 .Fn getw
  90 function
  91 obtains the next
  92 .Vt int
  93 (if present)
  94 from the stream pointed at by
  95 .Fa stream .
  96 .Pp
  97 The
  98 .Fn getc_unlocked
  99 and
 100 .Fn getchar_unlocked
 101 functions are equivalent to
 102 .Fn getc
 103 and
 104 .Fn getchar
 105 respectively,
 106 except that the caller is responsible for locking the stream
 107 with
 108 .Xr flockfile 3
 109 before calling them.
 110 These functions may be used to avoid the overhead of locking the stream
 111 for each character, and to avoid input being dispersed among multiple
 112 threads reading from the same stream.
 113 .Sh RETURN VALUES
 114 If successful, these routines return the next requested object
 115 from the
 116 .Fa stream .
 117 Character values are returned as an
 118 .Vt "unsigned char"
 119 converted to an
 120 .Vt int .
 121 If the stream is at end-of-file or a read error occurs,
 122 the routines return
 123 .Dv EOF .
 124 The routines
 125 .Xr feof 3
 126 and
 127 .Xr ferror 3
 128 must be used to distinguish between end-of-file and error.
 129 If an error occurs, the global variable
 130 .Va errno
 131 is set to indicate the error.
 132 The end-of-file condition is remembered, even on a terminal, and all
 133 subsequent attempts to read will return
 134 .Dv EOF
 135 until the condition is cleared with
 136 .Xr clearerr 3 .
 137 .Sh SEE ALSO
 138 .Xr ferror 3 ,
 139 .Xr flockfile 3 ,
 140 .Xr fopen 3 ,
 141 .Xr fread 3 ,
 142 .Xr getwc 3 ,
 143 .Xr putc 3 ,
 144 .Xr ungetc 3
 145 .Sh STANDARDS
 146 The
 147 .Fn fgetc ,
 148 .Fn getc ,
 149 and
 150 .Fn getchar
 151 functions
 152 conform to
 153 .St -isoC .
 154 The
 155 .Fn getc_unlocked
 156 and
 157 .Fn getchar_unlocked
 158 functions conform to
 159 .St -p1003.1-2001 .
 160 .Sh BUGS
 161 Since
 162 .Dv EOF
 163 is a valid integer value,
 164 .Xr feof 3
 165 and
 166 .Xr ferror 3
 167 must be used to check for failure after calling
 168 .Fn getw .
 169 The size and byte order of an
 170 .Vt int
 171 varies from one machine to another, and
 172 .Fn getw
 173 is not recommended for portable applications.
 174 .Pp