Table of Contents
stringsext is a Unicode enhancement of the GNU strings tool with additional functionalities: stringsext recognizes Cyrillic, CJKV characters and other scripts in all supported multi-byte-encodings, while GNU strings fails in finding any of these scripts in UTF-16 and many other encodings.
stringsext is mainly useful for determining the Unicode content in binary data: It prints all graphic character sequences in FILE or stdin that are at least MIN bytes long.
Unlike GNU strings stringsext can be configured to search for valid characters not only in ASCII but also in many other input encodings, e.g.: utf-8, utf-16be, utf-16le, big5, euc-jp, koi8-r and many others. --list-encodings shows a list of valid encoding names based on the WHATWG Encoding Standard. When more than one encoding is specified, the scan is performed in different threads simultaneously.
When searching for UTF-16 encoded strings, 96% of all possible two byte sequences, interpreted as UTF-16 code unit, relate directly to Unicode code points. As a result, the probability of encountering valid Unicode characters in a random byte stream, interpreted as UTF-16, is also 96%. In order to reduce this big number of false positives, stringsext provides a parametrizable Unicode-block-filter. See --encodings option for more details.
stringsext reads its input data
from (multiple) FILEs. With no
FILE is given, or when
-”, it reads standard input
When invoked with
stringsext -e ascii”,
stringsext can be used as
GNU strings replacement.
Apply ASCII-Filter. After the string-findings had been
decoded into UTF-8, the ASCII-filter is one of the 4 filters
all string-findings have to pass before being printed. The
ASCII-filter is applied to Unicode characters in
U+0000..U+007F” only. The
filter parameter AF decides which of these codes will pass
the filter. AF is some 128 bit integer, where each bit is
mapped to one character in the above character-range,
e.g. the character “
will pass the filter only, if bit no. 32 (=0x20) is set. If
the filter is configured with bit no. 32 cleared, all
U+0020” will be
The integer AF is notated in hexadecimal with prefix
0x...”. For the most common
use-cases, predefined filters can be set: e.g. alias names
All-Ctrl+Wsp” are shorthand
terms for ASCII-filters “all codes, but no
control-codes” or “all codes, including
white-space, but no control-codes”. See the output of
--list-encodings” for more
details about filter-names.
Suppress all metadata in output.
stringsext” presents its
string-findings in one or more output-lines. Each line shows
some meta information before printing the finding itself.
See the section
Output Format” for more
information about metadata.
Show how command-line-options are interpreted. When set,
stringsext” prints an
exhaustive filter parameter synoptic. Can be used for
debugging to check how the present command-line-arguments
are interpreted or for documentation purpose. Does not run
Set (multiple) input search encodings.
Search for strings encoded as ENCNAME. Encoding names
ENCNAME are denoted following the
prints a list of available encodings.
Once the input is decoded to UTF-8, all characters
have to pass 4 additional filters before being
printed: MIN (see
and GREP (see
The values given here override - for this ENC only -
the default values given by
prints a list of predefined filter-names.
Print only findings having at least one character with
one of the 4 filters decoded output lines must pass before
being printed. “
checks for the presence of ASCII_CODE in the first
output-line of a string-finding. The ASCII-code can be given
as decimal or hexadecimal number. The latter starts with
0x...”. Useful values are
\) for path search.
Print a synopsis of available options and default values.
List available encodings as WHATWG-Encoding-Standard-names, predefined ASCII-filter and Unicode-Block-Filter alias names.
Print only strings at least MIN characters long. The string length is measured in Unicode-characters (codepoints). --help shows the default value.
Print to FILE instead of stdout.
Set the printed output-line-length in UTF-8 characters
(string-findings only, metadata excluded). The line-length
is limited by some internal buffer size value (see
OUTPUT_BUF_LEN” in source
code). A value “
set to “
The longer the line-length is, the fewer strings will be
wrapped to the next line. The downside with long output
lines is, that the scanner loses precision in locating the
Require all characters in a finding to originate from the
same Unicode block. This option helps to reduce false
positives, especially when scanning for UTF-16. When set,
stringsext” prints only
Unicode block homogenous strings. For example:
-u All -n 10 -r” finds a
sequence of at least 10 Cyrillic characters in a row or
finds at least 10 Greek characters in a row, whereas it
ignores strings with randomly Cyrillic-Greek mixed
characters. Technically, this option guarantees, that all
multibyte characters of a finding - decoded into UTF-8 -
start with the same leading byte.
Start offset NUM for the input-stream-byte-counter given as decimal or hexadecimal integer. This is useful when large input data is stored split in separate files and when these files are so big that they should be analysed in separate stringsext runs.
Note: in general, it is better to treat all input files in one run by listing them as command-line-parameter. Thus, stringsext concatenates the split input-files to one input-stream before analyzing it. This way it is able to even recognize split strings at the cutting edge between two input files.
Print the position of the decoded string. The position indicated as input-stream bytes-offset. The single character argument specifies the RADIX of the offset: o for octal, x for hexadecimal, or d for decimal.
Unicode-block-filter UBF applied after decoding to UTF-8.
The decoder first searches for validly encoded character
sequences in the input stream. Then, the sequence of valid
characters is decoded into a chunk of UTF-8 characters,
which has to pass 4 filters before being printed:
The Unicode-block-filter applies to all decoded UTF-8
> U+007f” and
can be parametrized with
which is a 64-bit integer given in hexadecimal, prepended
Every bit “
0..=63” maps to
one leading-byte’s code position in
0xC0..0xFF”, e.g. if bit 0
is set -> all characters with leading byte
0xC0” pass the filter; if
bit 1 is set -> all characters with leading byte
0xC1”, pass the filter.
Otherwise, the character is rejected. For example, to print
only Syriac, set UFB to
0x1000_0000” (bit number 29
set) and AF to “0x0”. This instructs the filter
to let pass only UTF-8 characters, whose leading byte is
0xDC”. Table 3 on page
shows UTF-8-leading-bytes and their codes.
Alternatively, predefined alias names for the most common
Unicode-blocks can be used:
Greek” and many others. See
the output of
--list-encodings” for more
predefined filter names.
Print version info and exit.
The way stringsext prints its
output can be configured with the following options:
--output-line-len”. The first
--no-metadata” controls if
metadata is presented printed, “
determines if and how the byte-counter is shown and the
--output-line-len" at what
byte position string-findings are wrapped to the next line.
stringsext’s output syntax is best illustrated by example. Consider the following screen-shot:
stringsext -t x -q 30 -e utf8,10 -e ascii,50 test.txt test-small.txt (1) (2) A 0 (a UTF-8) Who Moved My Cheese? (3) A <1e (a UTF-8) An A-Mazing Way To Deal With C (4) A >1e+ (a UTF-8) hange In (5) A <1e (b ascii) An A-Mazing Way To Deal With C (6) A >1e+ (b ascii) hange In (7) A 3c+ (a UTF-8) Your Work (8) A >3c (a UTF-8) And In Your Life (9) A 3c+ (b ascii) Your Work (10)
(3): The letter “
A” in the first
column indicates, that the input originates from the first input
B” denotes the second input file,
0” indicates, that the
Who Moved My Cheese?” was found
at position “
<1e” means, that the
An A-Mazing Way To Deal With C”
was found somewhere in
0x1..=0x1e”. In addition, the
implemented algorithm guarantees that the string-finding is never
more than 60 bytes (2*
-q 30) away from the
indicated position, here: “
(5): The string-finding “
continues the previous string, hence
+”, and is situated
>1e”, meaning somewhere in the
0x1f..=3b”. Here again, it
is guaranteed, that the string-finding is always fewer than 60
-q 30) away from
(a UTF-8)” indicates, that the
Who Moved My Cheese?” was found
by the first scanner “
b” refers to the second
scanner, here “
List available encodings and predefined filter names:
Search for UTF-8 and UTF-16 Big-Endian encoded strings:
stringsext -t x -e utf-8 -e utf-16be -- someimage.raw
The same, but read from “
cat someimage.raw | stringsext -t x -e utf-8 -e utf-16be -- -
Scan a non-file device:
stringsext -t x -e utf-8 -e utf-16be -- /dev/sda1
Reduce the number of false positives, when scanning for UTF-16LE or UTF-16BE encoded strings. In the following example we search for Cyrillic only:
stringsext -t x -e UTF-16le,,None,Cyrillic -- someimage.raw
Search for UTF-16LE encoded Arabic and the digits 0 to 9:
stringsext -t x -e UTF-16le,,0x3f000000000000,Arabic -- someimage.raw
Search for UTF-8 encoded Syriac and all ASCII, control-codes excluded:
stringsext -t x -e UTF-8,,All-Ctrl,0x10000000 -- someimage.raw
Combine Little-Endian and Big-Endian scanning:
stringsext -t x -e UTF-16be -e UTF-16le -- someimage.raw
Show the filter default values used in the above example:
stringsext -d -t x -e UTF-16be -e UTF-16le -- someimage.raw
Search for path-names and URLs in some disk-partition:
sudo stringsext -tx -e utf-8 -n 15 -g 47 -- /dev/disk/by-uuid/91C8-2721
sudo stringsext -tx -e utf-8,15,,,47 -- /dev/disk/by-uuid/91C8-2721
A valid string is a sequence of valid characters according to the encoding chosen with --encoding. A valid string may contain control characters and graphic (visible and human readable) characters. stringsext is a tool to extract graphic characters out of binary data streams.
Scanners are parametrized with the
--encoding ENC option. Multiple
scanners may operate in parallel. Their search field is divided
into input chunks of "2 *
--output-line-len" bytes (see source code
documentation for details).
Before being printed, valid strings must pass four different filter, whose filter criteria are defined with the parameters: MIN, AF, UBF or GREP (see above).
The ASCII-character GREP, searched with the
--grep_char” option, must appear
in the first “
bytes to be reliably found in long strings. Increase
--output-line-len” if you search
for very long strings.
stringsext version 2 uses the external library encoding_rs to decode the incoming stream. Compared to the previous library rust-encoding used in stringsext version 1, the current library has some shortcomings mainly due to the restrictive API policy of the encoding_rs project.
stringsext could be faster, if encoding_rs were extensible (rust-encoding was): feature request: ASCII-filter · Issue #46 · hsivonen/encoding_rs
stringsext’s location counter could be more precise if the encoder state were observable: Enhancement: get read access to the decoder’s inner state · Issue #48 · hsivonen/encoding_rs
list could be more up to date, if
encoding_rs’ list were
encoding lists public by getreu · Pull Request #47 ·
While being desirable, the stringsext project does not have the required resources to maintain a fork of encoding_rs.
Project website: https://github.com/getreu/stringsext
Copyright (C) 2016-2020 Jens Getreu
Licensed under either of
at your option.
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 licence, shall be dual licensed as above, without any additional terms or conditions. Licensed under the Apache Licence, Version 2.0 (the "Licence"); you may not use this file except in compliance with the Licence.