file(C)

file -- determine file type

Syntax

file [ -achLs ] [ -f ffile ] [ -m mfile ] argument ...

Description

file performs a series of tests on each argument in an attempt to classify it.

If argument appears to be an ASCII file, file examines the first 512 bytes and tries to guess its language.
If argument is an executable file (see a.out(FP)), file prints the version stamp, provided it is greater than 0. If this is a ELF executable file, file also reports whether the file is dynamically or statically linked, whether the executable was stripped, and whether the file contains debug information.
If argument is a core(FP) file, file identifies the command line that created the core file and the time that command was invoked.

The following options are supported:

-a: Reset the file access time to what it was prior to being accessed by file command. The invoking process must have write permission on the file.
-c: Check the magic(F) file for format errors. This validation is not normally carried out for reasons of efficiency. No file typing is performed under this option.
-f ffile: Take ffile to be a file containing the names of the files to be examined.
-h: Do not follow symbolic links. By default, file follows symbolic links.
-L: Follow symbolic links. If multiple -L and -h options are specified, all but the last is ignored.
-m mfile: Use mfile as the magic file.
-s: Print a less verbose report of ELF object file attributes.
-x: Do not report information about the process that generated a core file or detailed information about ELF object and executable files.

file uses the file /etc/magic to identify files that have some sort of ``magic number''; that is, any file containing a numeric or string constant that indicates its type.

The magic(F) manual page and the commentary at the beginning of /etc/magic explain its format.

Exit values

file returns the following values:

0: successful completion
>0: an error occurred

Differences between versions

The following features are supported only for SCO OpenServer Release 5.0.6 and later releases:

Display information for a core file identifying the command line that created it and the time of invocation.
Display information about an elf object or executable file identifying whether the file is linked dynamically or statically, whether the executable was stripped, and whether the file contains debug information.

Use the -x option to turn off these features so that file reports the same information as for earlier releases.

Files

/etc/magic: database of magic numbers
/usr/lib/nls/support/Unix/fr_FR.ISO8859-1/Unix/magic: localized database of magic numbers (French)
/usr/lib/nls/support/Unix/de_DE.ISO8859-1/Unix/magic: localized database of magic numbers (German)

Standards conformance

file is conformant with:

ISO/IEC DIS 99452:1992, Information technology Portable Operating System Interface (POSIX) Part 2: Shell and Utilities (IEEE Std 1003.21992);
AT&T SVID Issue 2;
X/Open CAE Specification, Commands and Utilities, Issue 4, 1992.