doc/dict.n


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
.TP 10
\fBstart\fR
.
The new access position will be \fIoffset\fR bytes from the start
of the underlying file or device.
.TP 10
\fBcurrent\fR
.
The new access position will be \fIoffset\fR bytes from the current
access position; a negative \fIoffset\fR moves the access position
backwards in the underlying file or device.
.TP 10
\fBend\fR
.
The new access position will be \fIoffset\fR bytes from the end of
the file or device.  A negative \fIoffset\fR places the access position
before the end of file, and a positive \fIoffset\fR places the access
position after the end of file.
.PP
The \fIorigin\fR argument defaults to \fBstart\fR.
.PP
The command flushes all buffered output for the channel before the command
returns, even if the channel is in non-blocking mode.
It also discards any buffered and unread input.
This command returns an empty string.
An error occurs if this command is applied to channels whose underlying
file or device does not support seeking.
.PP
Note that \fIoffset\fR values are byte offsets, not character
offsets.  Both \fBseek\fR and \fBtell\fR operate in terms of bytes,
not characters, unlike \fBread\fR.
.SH EXAMPLES
.PP
Read a file twice:
.PP
.CS
set f [open file.txt]
set data1 [read $f]
\fBseek\fR $f 0
set data2 [read $f]
close $f
# $data1 eq $data2 if the file wasn't updated
.CE
.PP
Read the last 10 bytes from a file:
.PP
.CS
set f [open file.data]
# This is guaranteed to work with binary data but
# may fail with other encodings...
fconfigure $f -translation binary
\fBseek\fR $f -10 end
set data [read $f 10]
close $f
.CE
.SH "SEE ALSO"
file(n), open(n), close(n), gets(n), tell(n), Tcl_StandardChannels(3)
.SH KEYWORDS
access position, file, seek
'\" Local Variables:
'\" mode: nroff
'\" fill-column: 78
'\" End: