xref: /freebsd/lib/libc/stdio/fgetln.3 (revision 380a989b3223d455375b4fae70fd0b9bdd43bafb)
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32.\"     @(#)fgetln.3	8.3 (Berkeley) 4/19/94
33.\"
34.Dd April 19, 1994
35.Dt FGETLN 3
36.Os
37.Sh NAME
38.Nm fgetln
39.Nd get a line from a stream
40.Sh SYNOPSIS
41.Fd #include <stdio.h>
42.Ft char *
43.Fn fgetln "FILE *stream" "size_t *len"
44.Sh DESCRIPTION
45The
46.Fn fgetln
47function
48returns a pointer to the next line from the stream referenced by
49.Fa stream .
50This line is
51.Em not
52a C string as it does not end with a terminating
53.Dv NUL
54character.
55The length of the line, including the final newline,
56is stored in the memory location to which
57.Fa len
58points.
59(Note, however, that if the line is the last
60in a file that does not end in a newline,
61the returned text will not contain a newline.)
62.Sh RETURN VALUES
63Upon successful completion a pointer is returned;
64this pointer becomes invalid after the next
65.Tn I/O
66operation on
67.Fa stream
68(whether successful or not)
69or as soon as the stream is closed.
70Otherwise,
71.Dv NULL
72is returned.
73The
74.Fn fgetln
75function
76does not distinguish between end-of-file and error; the routines
77.Xr feof 3
78and
79.Xr ferror 3
80must be used
81to determine which occurred.
82If an error occurs, the global variable
83.Va errno
84is set to indicate the error.
85The end-of-file condition is remembered, even on a terminal, and all
86subsequent attempts to read will return
87.Dv NULL
88until the condition is
89cleared with
90.Xr clearerr 3 .
91.Pp
92The text to which the returned pointer points may be modified,
93provided that no changes are made beyond the returned size.
94These changes are lost as soon as the pointer becomes invalid.
95.Sh ERRORS
96.Bl -tag -width [EBADF]
97.It Bq Er EBADF
98The argument
99.Fa stream
100is not a stream open for reading.
101.El
102.Pp
103The
104.Fn fgetln
105function
106may also fail and set
107.Va errno
108for any of the errors specified for the routines
109.Xr fflush 3 ,
110.Xr malloc 3 ,
111.Xr read 2 ,
112.Xr stat 2 ,
113or
114.Xr realloc 3 .
115.Sh SEE ALSO
116.Xr ferror 3 ,
117.Xr fgets 3 ,
118.Xr fopen 3 ,
119.Xr putc 3
120.Sh HISTORY
121The
122.Fn fgetln
123function first appeared in
124.Bx 4.4 .
125