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14 .TH HEAD 1 "Mar 4, 2013"
15 .SH NAME
16 head \- display first few lines of files
17 .SH SYNOPSIS
18 .SS "/usr/bin/head"
19 .LP
20 .nf
21 \fB/usr/bin/head\fR [\fB-q\fR] [\fB-v\fR] [\fB-number\fR ] [ \fB-n\fR \fInumber\fR ] [ \fB-c\fR \fInumber\fR] [\fIfilename\fR]...
22 .fi
24 .SS "ksh93"
25 .LP
26 .nf
27 \fBhead\fR [\fB-qv\fR] [\fB-n\fR \fIlines\fR] [\fB-c\fR \fIchars\fR] [\fB-s\fR \fIskip\fR] [\fIfilename\fR]...
28 .fi
30 .SH DESCRIPTION
31 .SS "/usr/bin/head"
32 .sp
33 .LP
34 The \fBhead\fR utility copies the first \fInumber\fR of lines of each
35 \fIfilename\fR to the standard output. If no \fIfilename\fR is given,
36 \fBhead\fR copies lines from the standard input. The default value of
37 \fInumber\fR is \fB10\fR lines. If \fB-c\fR is specified, \fBhead\fR
38 copies the first \fInumber\fR of bytes of each filename.
39 .sp
40 .LP
41 When more than one file is specified, the start of each file looks like:
42 .sp
43 .in +2
44 .nf
45 \fB==>\fR \fIfilename\fR \fB<==\fR
46 .fi
47 .in -2
49 .sp
50 .LP
51 Thus, a common way to display a set of short files, identifying each one, is:
52 .sp
53 .in +2
54 .nf
55 example% \fBhead -9999 filename1 filename2 ...\fR
56 .fi
57 .in -2
58 .sp
60 .SS "ksh93"
61 .sp
62 .LP
63 The \fBhead\fR built-in in \fBksh93\fR is associated with the \fB/bin\fR and
64 \fB/usr/bin\fR paths. It is invoked when \fBhead\fR is executed without a
65 pathname prefix and the pathname search finds a \fB/bin/head\fR or
66 \fB/usr/bin/head\fR executable.
67 .sp
68 .LP
69 \fBhead\fR copies one or more input files to standard output, stopping at a
70 designated point for each file or to the end of the file whichever comes first.
71 Copying ends at the point indicated by the options. By default, a header of the
72 form \fB==> filename <==\fR is output before all but the first file but this
73 can be changed with the \fB-q\fR and \fB-v\fR options. If no file is given, or
74 if the file is \fB-\fR, \fBhead\fR copies from standard input starting at the
75 current location.
76 .sp
77 .LP
78 The option argument for \fB-c\fR and \fB-s\fR can optionally be followed by one
79 of the following characters to specify a different unit other than a single
80 byte:
81 .sp
82 .ne 2
83 .na
84 \fB\fBb\fR\fR
85 .ad
86 .RS 5n
87 512 bytes
88 .RE
90 .sp
91 .ne 2
92 .na
93 \fB\fBk\fR\fR
94 .ad
95 .RS 5n
96 1-kilobyte
97 .RE
99 .sp
100 .ne 2
101 .na
102 \fB\fBm\fR\fR
103 .ad
104 .RS 5n
105 1-megabyte
106 .RE
108 .sp
109 .LP
110 For backwards compatibility, \fB-number\fR is equivalent to \fB-n\fR number.
111 .SH OPTIONS
112 .SS "/usr/bin/head"
113 .sp
114 .LP
115 The following options are supported by \fB/usr/bin/head\fR:
116 .sp
117 .ne 2
118 .na
119 \fB\fB-n\fR \fInumber\fR\fR
120 .ad
121 .RS 13n
122 The first \fInumber\fR lines of each input file is copied to standard output.
123 The \fInumber\fR option-argument must be a positive decimal integer.
124 .RE
126 .sp
127 .ne 2
128 .na
129 \fB\fB-c\fR \fInumber\fR\fR
130 .ad
131 .RS 13n
132 The first \fInumber\fR bytes of each input file is copied to standard output.
133 The \fInumber\fR option-argument must be a positive decimal integer. Note,
134 output may end in the middle of a character if a file contains multi-byte
135 characters.
136 .RE
138 .sp
139 .ne 2
140 .na
141 \fB\fB-\fR\fInumber\fR\fR
142 .ad
143 .RS 13n
144 The \fInumber\fR argument is a positive decimal integer with the same effect as
145 the \fB-n\fR \fInumber\fR option.
146 .RE
148 .sp
149 .ne 2
150 .na
151 \fB-q\fR
152 .ad
153 .RS 13n
154 \fBhead\fR will not print a header in between each specified file.
155 .RE
157 .sp
158 .ne 2
159 .na
160 \fB-v\fR
161 .ad
162 .RS 13n
163 \fBhead\fR will always print a header in between each specified file.
164 .RE
166 .sp
167 .LP
168 If no options are specified, \fBhead\fR acts as if \fB-n\fR \fB10\fR had been
169 specified.
170 .SS "ksh93"
171 .sp
172 .LP
173 The following options are supported by the head built-in command in
174 \fBksh93\fR:
175 .sp
176 .ne 2
177 .na
178 \fB\fB-n\fR\fR
179 .ad
180 .br
181 .na
182 \fB\fB--lines=\fR\fIlines\fR\fR
183 .ad
184 .RS 18n
185 Copy lines from each file. The default value is \fB10\fR.
186 .RE
188 .sp
189 .ne 2
190 .na
191 \fB\fB-c\fR\fR
192 .ad
193 .br
194 .na
195 \fB\fB--bytes=\fR\fIchars\fR\fR
196 .ad
197 .RS 18n
198 Copy \fIchars\fR bytes from each file.
199 .RE
201 .sp
202 .ne 2
203 .na
204 \fB\fB-q\fR\fR
205 .ad
206 .br
207 .na
208 \fB\fB--quiet|silent\fR\fR
209 .ad
210 .RS 18n
211 Never output filename headers.
212 .RE
214 .sp
215 .ne 2
216 .na
217 \fB\fB-s\fR\fR
218 .ad
219 .br
220 .na
221 \fB\fB--skip=\fR\fIskip\fR\fR
222 .ad
223 .RS 18n
224 Skip \fIskip\fR characters or lines from each file before copying.
225 .RE
227 .sp
228 .ne 2
229 .na
230 \fB\fB-v\fR\fR
231 .ad
232 .br
233 .na
234 \fB\fB--verbose\fR\fR
235 .ad
236 .RS 18n
237 Always output filename headers.
238 .RE
240 .SH OPERANDS
241 .sp
242 .LP
243 The following operand is supported:
244 .sp
245 .ne 2
246 .na
247 \fB\fB\fIfilename\fR\fR\fR
248 .ad
249 .RS 12n
250 A path name of an input file. If no \fIfile\fR operands are specified, the
251 standard input is used.
252 .RE
254 .SH USAGE
255 .sp
256 .LP
257 See \fBlargefile\fR(5) for the description of the behavior of \fBhead\fR when
258 encountering files greater than or equal to 2 Gbyte ( 2^31 bytes).
259 .SH EXAMPLES
260 .LP
261 \fBExample 1 \fRWriting the First Ten Lines of All Files
262 .sp
263 .LP
264 The following example writes the first ten lines of all files, except those
265 with a leading period, in the directory:
267 .sp
268 .in +2
269 .nf
270 example% \fBhead *\fR
271 .fi
272 .in -2
273 .sp
275 .SH ENVIRONMENT VARIABLES
276 .sp
277 .LP
278 See \fBenviron\fR(5) for descriptions of the following environment variables
279 that affect the execution of \fBhead\fR: \fBLANG\fR, \fBLC_ALL\fR,
280 \fBLC_CTYPE\fR, \fBLC_MESSAGES\fR, and \fBNLSPATH\fR.
281 .SH EXIT STATUS
282 .sp
283 .LP
284 The following exit values are returned:
285 .sp
286 .ne 2
287 .na
288 \fB\fB0\fR\fR
289 .ad
290 .RS 6n
291 Successful completion.
292 .RE
294 .sp
295 .ne 2
296 .na
297 \fB\fB>0\fR\fR
298 .ad
299 .RS 6n
300 An error occurred.
301 .RE
303 .SH ATTRIBUTES
304 .sp
305 .LP
306 See \fBattributes\fR(5) for descriptions of the following attributes:
307 .SS "/usr/bin/head"
308 .sp
310 .sp
311 .TS
312 box;
313 c | c
314 l | l .
315 ATTRIBUTE TYPE ATTRIBUTE VALUE
316 _
317 CSI Enabled
318 _
319 Interface Stability Committed
320 _
321 Standard See \fBstandards\fR(5).
322 .TE
324 .SS "ksh93"
325 .sp
327 .sp
328 .TS
329 box;
330 c | c
331 l | l .
332 ATTRIBUTE TYPE ATTRIBUTE VALUE
333 _
334 Interface Stability See below.
335 .TE
337 .sp
338 .LP
339 The \fBksh93\fR built-in binding to \fB/bin\fR and \fB/usr/bin\fR is Volatile.
340 The built-in interfaces are Uncommitted.
341 .SH SEE ALSO
342 .sp
343 .LP
344 \fBcat\fR(1), \fBksh93\fR(1), \fBmore\fR(1), \fBpg\fR(1), \fBtail\fR(1),
345 \fBattributes\fR(5), \fBenviron\fR(5), \fBlargefile\fR(5), \fBstandards\fR(5)