xref: /freebsd/usr.bin/tail/tail.1 (revision 380a989b3223d455375b4fae70fd0b9bdd43bafb)
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35.\"	@(#)tail.1	8.1 (Berkeley) 6/6/93
36.\"
37.Dd June 6, 1993
38.Dt TAIL 1
39.Os BSD 4
40.Sh NAME
41.Nm tail
42.Nd display the last part of a file
43.Sh SYNOPSIS
44.Nm
45.Oo
46.Fl F |
47.Fl f |
48.Fl r
49.Oc
50.Oo
51.Fl b Ar number |
52.Fl c Ar number |
53.Fl n Ar number
54.Oc
55.Op Ar
56.Sh DESCRIPTION
57The
58.Nm
59utility displays the contents of
60.Ar file
61or, by default, its standard input, to the standard output.
62.Pp
63The display begins at a byte, line or 512-byte block location in the
64input.
65Numbers having a leading plus (``+'') sign are relative to the beginning
66of the input, for example,
67.Dq -c +2
68starts the display at the second
69byte of the input.
70Numbers having a leading minus (``-'') sign or no explicit sign are
71relative to the end of the input, for example,
72.Dq -n 2
73displays the last two lines of the input.
74The default starting location is
75.Dq -n 10 ,
76or the last 10 lines of the input.
77.Pp
78The options are as follows:
79.Bl -tag -width Ds
80.It Fl b Ar number
81The location is
82.Ar number
83512-byte blocks.
84.It Fl c Ar number
85The location is
86.Ar number
87bytes.
88.It Fl f
89The
90.Fl f
91option causes
92.Nm
93to not stop when end of file is reached, but rather to wait for additional
94data to be appended to the input.
95The
96.Fl f
97option is ignored if the standard input is a pipe, but not if it is a FIFO.
98.It Fl F
99The
100.Fl F
101option implies the
102.Fl f
103option, but
104.Nm
105will also check to see if the file being followed has been renamed or rotated.
106The file is closed and reopened when
107.Nm
108detects that the filename being read from has a new inode number.
109The
110.Fl F
111option is ignored if reading from standard input rather than a file.
112.It Fl n Ar number
113The location is
114.Ar number
115lines.
116.It Fl r
117The
118.Fl r
119option causes the input to be displayed in reverse order, by line.
120Additionally, this option changes the meaning of the
121.Fl b ,
122.Fl c
123and
124.Fl n
125options.
126When the
127.Fl r
128option is specified, these options specify the number of bytes, lines
129or 512-byte blocks to display, instead of the bytes, lines or blocks
130from the beginning or end of the input from which to begin the display.
131The default for the
132.Fl r
133option is to display all of the input.
134.El
135.Pp
136If more than a single file is specified, each file is preceded by a
137header consisting of the string
138.Dq ==> XXX <==
139where
140.Dq XXX
141is the name of the file.
142.Pp
143The
144.Nm
145utility exits 0 on success, and >0 if an error occurs.
146.Sh SEE ALSO
147.Xr cat 1 ,
148.Xr head 1 ,
149.Xr sed 1
150.Sh STANDARDS
151The
152.Nm
153utility is expected to be a superset of the
154.St -p1003.2-92
155specification.
156In particular, the
157.Fl F ,
158.Fl b
159and
160.Fl r
161options are extensions to that standard.
162.Pp
163The historic command line syntax of
164.Nm
165is supported by this implementation.
166The only difference between this implementation and historic versions
167of
168.Nm tail ,
169once the command line syntax translation has been done, is that the
170.Fl b ,
171.Fl c
172and
173.Fl n
174options modify the
175.Fl r
176option, i.e. ``-r -c 4'' displays the last 4 characters of the last line
177of the input, while the historic tail (using the historic syntax ``-4cr'')
178would ignore the
179.Fl c
180option and display the last 4 lines of the input.
181.Sh HISTORY
182A
183.Nm
184command appeared in
185.At v7 .
186