Strings (Unix): Difference between revisions

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{{Short description|Shell command for extracting printable text from a binary file}}

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<code>'''strings'''</code> is a [[Shell (computing)|shell command]] that extracts [[printable character]] [[String (computer science)|strings]] from a [[computer file|file]] {{endash}} which is particular useful for analyzing the content of a [[binary file]]. By definition, a binary file contains data that is not printable text yet a binary file often does contain some printable character text {{endash}} often in relatively short sequences distributed throughout the file. These portions of the binary file can be informative as to what the file contains overall. For a [[text file]], a file containing all printable characters, the command prints the entire file content, and therefore, provides no utility over more commonly used file output commands such as <code>[[cat (Unix)|cat]]</code>.

In [[computer software]], '''strings''' is a program in [[Unix]], [[Plan 9 from Bell Labs|Plan 9]], [[Inferno (operating system)|Inferno]], and [[Unix-like]] [[operating system]]s that finds and prints the strings of printable characters in files. The files can be of regular text files or [[binary files]] such as executables. It can be used on object files and [[core dump]]s. '''strings''' is mainly useful for determining the contents of non-text files.

The command searches for sequences of printable characters that end with a [[null-terminated string|NUL character]] but ignores any sequence that is less than a specified length or 4 characters by default. Some implementations provide options for determining what is recognized as a printable character, which is useful for finding non-[[ASCII]] and [[wide character]] text. By default, it only selects strings from the initialized and loaded sections of an object file. For other types of files, it selects strings from the whole file.

==Overview==

Strings are recognized by looking for sequences of at least 4 (by default) printable characters terminating in a NUL character (that is, [[null-terminated string]]s).

Some implementations provide options for determining what is recognized as a printable character, which is useful for finding non-ASCII and wide character text.

By default, it only prints the strings from the initialized and loaded sections of object files; for other types of files, it prints the strings from the whole file.

With regular text files, '''strings''' and [[Cat_(Unix)|cat]] give different output.

[[Cat_(Unix)|cat]] outputs the non printable characters but '''strings''' does not.

'''strings'''The command is available in [[Unix]], [[Plan 9 from Bell Labs|Plan 9]], [[Inferno (operating system)|Inferno]], and [[Unix-like]] systems. It is part of the [[GNU Binary Utilities]] ({{mono|binutils}}), and has been portedimplemented toin other operating systems including [[Microsoft Windows|Windows]].<ref>[[cygwin]]</ref>

==Example==

Using ''strings'' to print sequences of characters that are at least 8 characters long (this command prints the system's [[BIOS]] information; should be run as root):

The following command searches the system's [[BIOS]] for strings that are at 8 characters long:

dd if=/dev/mem bs=1k skip=768 count=256 2>[[/dev/null]] | strings -n 8 | [[less (Unix)|less]]

dd if=/dev/mem bs=1k skip=768 count=256 2>[[/dev/null]] | strings -n 8 | [[less (Unix)|less]]

==See also==

{{Portal|Free and open-source software}}

* [[{{Annotated link|GNU Debugger]]}}

* [[Cat (Unix)]]

* {{Annotated link|List of POSIX commands}}

* [[{{Annotated link|Paste (Unix)]]}}

* [[GNU Debugger]]

* [[{{Annotated link|Strip (Unix)]]}}

==References==