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10 .TH FPUTC 3C "May 13, 2017"
11 .SH NAME
12 fputc, putc, putc_unlocked, putchar, putchar_unlocked, putw \- put a byte on a
13 stream
14 .SH SYNOPSIS
15 .LP
16 .nf
17 #include <stdio.h>
19 \fBint\fR \fBfputc\fR(\fBint\fR \fIc\fR, \fBFILE *\fR\fIstream\fR);
20 .fi
22 .LP
23 .nf
24 \fBint\fR \fBputc\fR(\fBint\fR \fIc\fR, \fBFILE *\fR\fIstream\fR);
25 .fi
27 .LP
28 .nf
29 \fBint\fR \fBputc_unlocked\fR(\fBint\fR \fIc\fR, \fBFILE *\fR\fIstream\fR);
30 .fi
32 .LP
33 .nf
34 \fBint\fR \fBputchar\fR(\fBint\fR \fIc\fR);
35 .fi
37 .LP
38 .nf
39 \fBint\fR \fBputchar_unlocked\fR(\fBint\fR \fIc\fR);
40 .fi
42 .LP
43 .nf
44 \fBint\fR \fBputw\fR(\fBint\fR \fIw\fR, \fBFILE *\fR\fIstream\fR);
45 .fi
47 .SH DESCRIPTION
48 .LP
49 The \fBfputc()\fR function writes the byte specified by \fIc\fR (converted to
50 an \fBunsigned char\fR) to the output stream pointed to by \fIstream\fR, at the
51 position indicated by the associated file-position indicator for the stream (if
52 defined), and advances the indicator appropriately. If the file cannot support
53 positioning requests, or if the stream was opened with append mode, the byte is
54 appended to the output stream.
55 .sp
56 .LP
57 The \fBst_ctime\fR and \fBst_mtime\fR fields of the file will be marked for
58 update between the successful execution of \fBfputc()\fR and the next
59 successful completion of a call to \fBfflush\fR(3C) or \fBfclose\fR(3C) on the
60 same stream or a call to \fBexit\fR(3C) or \fBabort\fR(3C).
61 .sp
62 .LP
63 The \fBputc()\fR routine behaves like \fBfputc()\fR, except that it is
64 implemented as a macro. It runs faster than \fBfputc()\fR, but it takes up more
65 space per invocation and its name cannot be passed as an argument to a function
66 call.
67 .sp
68 .LP
69 The call \fBputchar(\fR\fIc\fR\fB)\fR is equivalent to \fBputc(\fR\fIc\fR\fB,
70 \fR\fIstdout\fR\fB).\fR The \fBputchar()\fR routine is implemented as a macro.
71 .sp
72 .LP
73 The \fBputc_unlocked()\fR and \fBputchar_unlocked()\fR routines are variants of
74 \fBputc()\fR and \fBputchar()\fR, respectively, that do not lock the stream.
75 It is the caller's responsibility to acquire the stream lock before calling
76 these routines and releasing the lock afterwards; see \fBflockfile\fR(3C) and
77 \fBstdio\fR(3C). These routines are implemented as macros.
78 .sp
79 .LP
80 The \fBputw()\fR function writes the word (that is, type \fBint\fR) \fIw\fR to
81 the output \fIstream\fR (at the position at which the file offset, if defined,
82 is pointing). The size of a word is the size of a type \fBint\fR and varies
83 from machine to machine. The \fBputw()\fR function neither assumes nor causes
84 special alignment in the file.
85 .sp
86 .LP
87 The \fBst_ctime\fR and \fBst_mtime\fR fields of the file will be marked for
88 update between the successful execution of \fBputw()\fR and the next successful
89 completion of a call to \fBfflush\fR(3C) or \fBfclose\fR(3C) on the same stream
90 or a call to \fBexit\fR(3C) or \fBabort\fR(3C).
91 .SH RETURN VALUES
92 .LP
93 Upon successful completion, \fBfputc()\fR, \fBputc()\fR, \fBputc_unlocked()\fR,
94 \fBputchar()\fR, and \fBputchar_unlocked()\fR return the value that was
95 written. Otherwise, these functions return EOF, the error indicator for the
96 stream is set, and \fBerrno\fR is set to indicate the error.
97 .sp
98 .LP
99 Upon successful completion, \fBputw()\fR returns \fB0\fR. Otherwise, it returns
100 a non-zero value, sets the error indicator for the associated \fIstream\fR, and
101 sets \fBerrno\fR to indicate the error.
102 .sp
103 .LP
104 An unsuccessful completion will occur, for example, if the file associated with
105 \fIstream\fR is not open for writing or if the output file cannot grow.
106 .SH ERRORS
107 .LP
108 The \fBfputc()\fR, \fBputc()\fR, \fBputc_unlocked()\fR, \fBputchar()\fR,
109 \fBputchar_unlocked()\fR, and \fBputw()\fR functions will fail if either the
110 \fIstream\fR is unbuffered or the \fIstream\fR's buffer needs to be flushed,
111 and:
112 .sp
113 .ne 2
114 .na
115 \fB\fBEAGAIN\fR\fR
116 .ad
117 .RS 10n
118 The \fBO_NONBLOCK\fR flag is set for the file descriptor underlying
119 \fIstream\fR and the process would be delayed in the write operation.
120 .RE
122 .sp
123 .ne 2
124 .na
125 \fB\fBEBADF\fR\fR
126 .ad
127 .RS 10n
128 The file descriptor underlying \fIstream\fR is not a valid file descriptor open
129 for writing.
130 .RE
132 .sp
133 .ne 2
134 .na
135 \fB\fBEFBIG\fR\fR
136 .ad
137 .RS 10n
138 An attempt was made to write to a file that exceeds the maximum file size or
139 the process' file size limit.
140 .RE
142 .sp
143 .ne 2
144 .na
145 \fB\fBEFBIG\fR\fR
146 .ad
147 .RS 10n
148 The file is a regular file and an attempt was made to write at or beyond the
149 offset maximum.
150 .RE
152 .sp
153 .ne 2
154 .na
155 \fB\fBEINTR\fR\fR
156 .ad
157 .RS 10n
158 The write operation was terminated due to the receipt of a signal, and no data
159 was transferred.
160 .RE
162 .sp
163 .ne 2
164 .na
165 \fB\fBEIO\fR\fR
166 .ad
167 .RS 10n
168 A physical I/O error has occurred, or the process is a member of a background
169 process group attempting to write to its controlling terminal, \fBTOSTOP\fR is
170 set, the process is neither ignoring nor blocking \fBSIGTTOU\fR and the process
171 group of the process is orphaned. This error may also be returned under
172 implementation-dependent conditions.
173 .RE
175 .sp
176 .ne 2
177 .na
178 \fB\fBENOSPC\fR\fR
179 .ad
180 .RS 10n
181 There was no free space remaining on the device containing the file.
182 .RE
184 .sp
185 .ne 2
186 .na
187 \fB\fBEPIPE\fR\fR
188 .ad
189 .RS 10n
190 An attempt is made to write to a pipe or \fBFIFO\fR that is not open for
191 reading by any process. A \fBSIGPIPE\fR signal will also be sent to the calling
192 thread.
193 .RE
195 .sp
196 .LP
197 The \fBfputc()\fR, \fBputc()\fR, \fBputc_unlocked()\fR, \fBputchar()\fR,
198 \fBputchar_unlocked()\fR, and \fBputw()\fR functions may fail if:
199 .sp
200 .ne 2
201 .na
202 \fB\fBENOMEM\fR\fR
203 .ad
204 .RS 10n
205 Insufficient storage space is available.
206 .RE
208 .sp
209 .ne 2
210 .na
211 \fB\fBENXIO\fR\fR
212 .ad
213 .RS 10n
214 A request was made of a non-existent device, or the request was outside the
215 capabilities of the device.
216 .RE
218 .SH USAGE
219 .LP
220 Functions exist for the \fBputc()\fR, \fBputc_unlocked()\fR, \fBputchar()\fR,
221 and \fBputchar_unlocked()\fR macros. To get the function form, the macro name
222 must be undefined (for example, \fB#undef putc\fR).
223 .sp
224 .LP
225 When the macro forms are used, \fBputc()\fR and \fBputc_unlocked()\fR evaluate
226 the \fIstream\fR argument more than once. In particular, \fBputc(\fR\fIc\fR\fB,
227 \fR\fI*f++\fR\fB);\fR does not work sensibly. The \fBfputc()\fR function
228 should be used instead when evaluating the \fIstream\fR argument has side
229 effects.
230 .sp
231 .LP
232 Because of possible differences in word length and byte ordering, files written
233 using \fBputw()\fR are implementation-dependent, and possibly cannot be read
234 using \fBgetw\fR(3C) by a different application or by the same application
235 running in a different environment.
236 .sp
237 .LP
238 The \fBputw()\fR function is inherently byte stream oriented and is not tenable
239 in the context of either multibyte character streams or wide-character streams.
240 Application programmers are encouraged to use one of the character-based output
241 functions instead.
242 .SH ATTRIBUTES
243 .LP
244 See \fBattributes\fR(5) for descriptions of the following attributes:
245 .sp
247 .sp
248 .TS
249 box;
250 c | c
251 l | l .
252 ATTRIBUTE TYPE ATTRIBUTE VALUE
253 _
254 Interface Stability T{
255 \fBfputc()\fR, \fBputc()\fR, \fBputc_unlocked()\fR, \fBputchar()\fR, and \fBputchar_unlocked()\fR are Standard.
256 T}
257 _
258 MT-Level See \fBNOTES\fR below.
259 .TE
261 .SH SEE ALSO
262 .LP
263 \fBgetrlimit\fR(2), \fBulimit\fR(2) \fBwrite\fR(2), \fBIntro\fR(3),
264 \fBabort\fR(3C), \fBexit\fR(3C), \fBfclose\fR(3C), \fBferror\fR(3C),
265 \fBfflush\fR(3C), \fBflockfile\fR(3C), \fBprintf\fR(3C),
266 \fBputc\fR(3C), \fBputs\fR(3C), \fBsetbuf\fR(3C), \fBstdio\fR(3C),
267 \fBattributes\fR(5), \fBstandards\fR(5)
268 .SH NOTES
269 .LP
270 The \fBfputc()\fR, \fBputc()\fR, \fBputchar()\fR, and \fBputw()\fR routines are
271 MT-Safe in multithreaded applications. The \fBputc_unlocked()\fR and
272 \fBputchar_unlocked()\fR routines are unsafe in multithreaded applications.