Note that a "lazy" parser is used which does not check for more than the first option letter, unless the option is followed by a parameter. Spaces between a single option letter and its parameter are optional. Parameters to options can be specified in decimal, hexadecimal or octal notation. Thus -c8, -c 8, -c 010 and -cols 8 are all equivalent.
xxd -r has some builtin magic while evaluating line number information. If the output file is seekable, then the linenumbers at the start of each hexdump line may be out of order, lines may be missing, or overlapping. In these cases xxd will lseek(2) to the next position. If the output file is not seekable, only gaps are allowed, which will be filled by null-bytes.
xxd -r never generates parse errors. Garbage is silently skipped.
When editing hexdumps, please note that xxd -r skips everything on the input line after reading enough columns of hexadecimal data (see option -c). This also means, that changes to the printable ascii (or ebcdic) columns are always ignored. Reverting a plain (or postscript) style hexdump with xxd -r -p does not depend on the correct number of columns. Here anything that looks like a pair of hex-digits is interpreted.
Note the difference between
% xxd -i file
and
% xxd -i < file
xxd -s +seek may be different from xxd -s seek, as lseek(2) is used to "rewind" input. A '+' makes a difference if the input source is stdin, and if stdin's file position is not at the start of the file by the time xxd is started and given its input. The following examples may help to clarify (or further confuse!)...
Rewind stdin before reading; needed because the `cat' has already read to the
end of stdin.
% sh -c "cat > plain_copy; xxd -s 0 > hex_copy" < file
Hexdump from file position 0x480 (=1024+128) onwards.
The `+' sign means "relative to the current position", thus the `128' adds to
the 1k where dd left off.
% sh -c "dd of=plain_snippet bs=1k count=1; xxd -s +128 > hex_snippet" < file
Hexdump from file position 0x100 ( = 1024-768) on.
% sh -c "dd of=plain_snippet bs=1k count=1; xxd -s +-768 > hex_snippet" < file
However, this is a rare situation and the use of `+' is rarely needed. The author prefers to monitor the effect of xxd with strace(1) or truss(1), whenever -s is used.
Print everything but the first three lines (hex 0x30 bytes) of
file.
% xxd -s 0x30 file
Print 3 lines (hex 0x30 bytes) from the end of
file.
% xxd -s -0x30 file
Print 120 bytes as continuous hexdump with 20 octets per line.
% xxd -l 120 -ps -c 20 xxd.1
2e54482058584420312022417567757374203139
39362220224d616e75616c207061676520666f72
20787864220a2e5c220a2e5c222032317374204d
617920313939360a2e5c22204d616e2070616765
20617574686f723a0a2e5c2220202020546f6e79
204e7567656e74203c746f6e79407363746e7567
Hexdump the first 120 bytes of this man page with 12 octets per line.
% xxd -l 120 -c 12 xxd.1
0000000: 2e54 4820 5858 4420 3120 2241 .TH XXD 1 "A
000000c: 7567 7573 7420 3139 3936 2220 ugust 1996"
0000018: 224d 616e 7561 6c20 7061 6765 "Manual page
0000024: 2066 6f72 2078 7864 220a 2e5c for xxd"..\
0000030: 220a 2e5c 2220 3231 7374 204d "..\" 21st M
000003c: 6179 2031 3939 360a 2e5c 2220 ay 1996..\"
0000048: 4d61 6e20 7061 6765 2061 7574 Man page aut
0000054: 686f 723a 0a2e 5c22 2020 2020 hor:..\"
0000060: 546f 6e79 204e 7567 656e 7420 Tony Nugent
000006c: 3c74 6f6e 7940 7363 746e 7567 <tony@sctnug
Display just the date from the file xxd.1
% xxd -s 0x36 -l 13 -c 13 xxd.1
0000036: 3231 7374 204d 6179 2031 3939 36 21st May 1996
Copy
input_file
to
output_file
and prepend 100 bytes of value 0x00.
% xxd input_file | xxd -r -s 100 > output_file
Patch the date in the file xxd.1
% echo "0000037: 3574 68" | xxd -r - xxd.1
% xxd -s 0x36 -l 13 -c 13 xxd.1
0000036: 3235 7468 204d 6179 2031 3939 36 25th May 1996
Create a 65537 byte file with all bytes 0x00,
except for the last one which is 'A' (hex 0x41).
% echo "010000: 41" | xxd -r > file
Hexdump this file with autoskip.
% xxd -a -c 12 file
0000000: 0000 0000 0000 0000 0000 0000 ............
*
000fffc: 0000 0000 40 ....A
Create a 1 byte file containing a single 'A' character.
The number after '-r -s' adds to the linenumbers found in the file;
in effect, the leading bytes are suppressed.
% echo "010000: 41" | xxd -r -s -0x10000 > file
Use xxd as a filter within an editor such as
vim(1)
to hexdump a region marked between `a' and `z'.
:'a,'z!xxd
Use xxd as a filter within an editor such as
vim(1)
to recover a binary hexdump marked between `a' and `z'.
:'a,'z!xxd -r
Use xxd as a filter within an editor such as
vim(1)
to recover one line of a hexdump. Move the cursor over the line and type:
!!xxd -r
Read single characters from a serial line
% xxd -c1 < /dev/term/b &
% stty < /dev/term/b -echo -opost -isig -icanon min 1
% echo -n foo > /dev/term/b
Distribute freely and credit me,
make money and share with me,
lose money and don't ask me.
Manual page started by Tony Nugent
<tony@sctnugen.ppp.gu.edu.au> <T.Nugent@sct.gu.edu.au>
Small changes by Bram Moolenaar.
Edited by Juergen Weigert.