stdio/fgets.3

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  36 .\"     @(#)fgets.3     8.1 (Berkeley) 6/4/93
  37 .\" $FreeBSD: src/lib/libc/stdio/fgets.3,v 1.12 2001/10/01 16:08:59 ru Exp $
  38 .\"
  39 .Dd June 4, 1993
  40 .Dt FGETS 3
  41 .Os
  42 .Sh NAME
  43 .Nm fgets ,
  44 .Nm gets
  45 .Nd get a line from a stream
  46 .Sh LIBRARY
  47 .Lb libc
  48 .Sh SYNOPSIS
  49 .In stdio.h
  50 .Ft char *
  51 .Fn fgets "char *str" "int size" "FILE *stream"
  52 .Ft char *
  53 .Fn gets "char *str"
  54 .Sh DESCRIPTION
  55 The
  56 .Fn fgets
  57 function
  58 reads at most one less than the number of characters specified by
  59 .Fa size
  60 from the given
  61 .Fa stream
  62 and stores them in the string
  63 .Fa str .
  64 Reading stops when a newline character is found,
  65 at end-of-file or error.
  66 The newline, if any, is retained.
  67 If any characters are read and there is no error, a
  68 .Ql \e0
  69 character is appended to end the string.
  70 .Pp
  71 The
  72 .Fn gets
  73 function
  74 is equivalent to
  75 .Fn fgets
  76 with an infinite
  77 .Fa size
  78 and a
  79 .Fa stream
  80 of
  81 .Em stdin ,
  82 except that the newline character (if any) is not stored in the string.
  83 It is the caller's responsibility to ensure that the input line,
  84 if any, is sufficiently short to fit in the string.
  85 .Sh RETURN VALUES
  86 Upon successful completion,
  87 .Fn fgets
  88 and
  89 .Fn gets
  90 return
  91 a pointer to the string.
  92 If end-of-file occurs before any characters are read,
  93 they return
  94 .Dv NULL
  95 and the buffer contents is unchanged.
  96 If an error occurs,
  97 they return
  98 .Dv NULL
  99 and the buffer contents is indeterminate.
 100 The
 101 .Fn fgets
 102 and
 103 .Fn gets
 104 functions
 105 do not distinguish between end-of-file and error, and callers must use
 106 .Xr feof 3
 107 and
 108 .Xr ferror 3
 109 to determine which occurred.
 110 .Sh ERRORS
 111 .Bl -tag -width Er
 112 .It Bq Er EBADF
 113 The given
 114 .Fa stream
 115 is not a readable stream.
 116 .El
 117 .Pp
 118 The function
 119 .Fn fgets
 120 may also fail and set
 121 .Va errno
 122 for any of the errors specified for the routines
 123 .Xr fflush 3 ,
 124 .Xr fstat 2 ,
 125 .Xr read 2 ,
 126 or
 127 .Xr malloc 3 .
 128 .Pp
 129 The function
 130 .Fn gets
 131 may also fail and set
 132 .Va errno
 133 for any of the errors specified for the routine
 134 .Xr getchar 3 .
 135 .Sh SEE ALSO
 136 .Xr feof 3 ,
 137 .Xr ferror 3 ,
 138 .Xr fgetln 3
 139 .Sh STANDARDS
 140 The functions
 141 .Fn fgets
 142 and
 143 .Fn gets
 144 conform to
 145 .St -isoC .
 146 .Sh BUGS
 147 Since it is usually impossible to ensure that the next input line
 148 is less than some arbitrary length, and because overflowing the
 149 input buffer is almost invariably a security violation, programs
 150 should
 151 .Em NEVER
 152 use
 153 .Fn gets .
 154 The
 155 .Fn gets
 156 function
 157 exists purely to conform to
 158 .St -isoC .