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31 .Dd September 23, 2021
41 .Op Fl -ignore-initial Ns Cm = Ns Ar num1 Ns Op :num2
42 .Op Fl -bytes Ns Cm = Ns Ar num
44 .Op Ar skip1 Op Ar skip2
48 utility compares two files of any type and writes the results
49 to the standard output.
52 is silent if the files are the same; if they differ, the byte
53 and line number at which the first difference occurred is reported.
55 Bytes and lines are numbered beginning with one.
57 The following options are available:
58 .Bl -tag -width indent
59 .It Fl b , Fl -print-bytes
60 Print each byte when a difference is found.
62 Do not follow symbolic links.
63 .It Fl i Ar num1 Ns Oo :num2 Oc , Fl -ignore-initial= Ns Ar num1 Ns Op :num2
74 is not specified, then
80 .It Fl l , Fl -verbose
81 Print the byte number (decimal) and the differing
82 byte values (octal) for each difference.
83 .It Fl n Ar num , Fl -bytes= Ns num
87 .It Fl s , Fl -silent , Fl -quiet
88 Print nothing for differing files; return exit
93 but prints in hexadecimal and using zero as index
94 for the first byte in the files.
96 For regular files compare file sizes first, and fail the comparison if they
100 The optional arguments
104 are the byte offsets from the beginning of
108 respectively, where the comparison will begin.
109 The offset is decimal by default, but may be expressed as a hexadecimal
110 or octal value by preceding it with a leading ``0x'' or ``0''.
115 may also be specified with SI size suffixes.
119 utility exits with one of the following values:
122 The files are identical.
124 The files are different; this includes the case
125 where one file is identical to the first part of
127 In the latter case, if the
129 option has not been specified,
131 writes to standard error that EOF was reached in the shorter
132 file (before any differences were found).
137 Assuming a file named
139 with the following contents:
140 .Bd -literal -offset indent
148 .Bd -literal -offset indent
149 $ echo -e "a\\nb\\nc" | cmp - example.txt
152 Same as above but introducing a change in the third byte of stdin.
153 Show the byte number (decimal) and differing byte (octal):
154 .Bd -literal -offset indent
155 $ echo -e "a\\nR\\nc" | cmp -l - example.txt
159 Compare file sizes of
162 .Pa /boot/loader.conf
163 and return 1 if they are not equal.
166 can only be used with regular files:
167 .Bd -literal -offset indent
168 $ cmp -z example.txt /boot/loader.conf
169 example.txt /boot/loader.conf differ: size
174 omitting the first 4 bytes from stdin and the first 2 bytes from
176 .Bd -literal -offset indent
177 $ echo -e "a\\nR\\nb\\nc" | cmp - example.txt 4 2
185 utility is expected to be
196 options are extensions to the standard.
200 arguments are extensions to the standard.
209 above refers to the traditional power of two convention, as described in
210 .Xr expand_number 3 .