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