file — Determine file type

Format

file [–BcdEh] [–f filelist] [-M magic] [–m magic] [-W option[,option]...] file …file …

file -i [-h] [–f filelist] file …file …

Description

file determines the format of each file by inspecting the attributes and (for a regular file) reading the contents of the file. If the file is an executable, its addressing mode is determined for output. If file is not an executable, file compares each file to entries found in one or more magic files to determine their file type. If you specify - as a file name, file reads from the standard input (stdin).

file then divides files that do not match a template in the magic file into text files and binary data. Then, by reading the text files and making an informed guess based on the contents, file further divides text files into various types such as C programs, assembler programs, files of commands to the shell, and yacc or lex programs.

file displays the name of each file along with the file type.
  • If the variable _UNIX03=YES is set, a space is used to separate the file name and the type.
  • If the variable _UNIX03 is unset or is not set to YES, a tab is used to separate the file name and the file type.
The file utility uses three types of tests to determine the file type: the file attribute tests, the position-sensitive tests and the context-sensitive tests.
  • The "file attribute tests" determine file types such as directory, character special, FIFO, socket, symbolic link, and external link.
  • The "position-sensitive tests" determine file types by looking for certain string or binary values at specific offsets in the file being examined. The "default position-sensitive tests" are defined by:
    • The/etc/magic file
    • The AMODE test built into the file utility
    If a magic file test succeeds, the message field of the line will be printed and no further tests will be applied, except for tests on immediately following lines beginning with a single '>' character.
  • The "default context-sensitive tests" are built into the file utility. These tests look for language constructs in text files trying to identify shell scripts, C, FORTRAN, and other computer language source files, and even plain text files. The "default context-sensitive tests" will never be applied before any "position-sensitive tests" even if the -d option is specified before an -m magic option or -M magic option.

Options

–B
Disables the automatic conversion of tagged files. This option is ignored if the filecodeset or pgmcodeset options (-W option) are specified.
–c
Only checks the file magic (specified by -m or -M) and /etc/magic. If the semantics imply it, see the usage notes for the validity of the format.
-d
Apply any default position-sensitive tests and default context-sensitive tests to the file. This option is the default if no -M or -m option is specified. See the usage notes for more information.
-E
Uses the magic file and bypasses the checking of regular files for executables.
–f filelist
Examines the files listed in the file filelist.
-h
When a symbolic link is encountered, identify file as a symbolic link instead of following the link.
If -h is not specified and
  • file is an external link or file is a symbolic link referring to a nonexistent file:
    If the variable _UNIX03=YES is set
    The type will be reported as if -h was specified.
    If the variable _UNIX03 is unset or is not set to YES
    The type will be reported as if -h was not specified.

-i
If file is a regular file, does not attempt to classify the type of the file further. This option can only be used with -h and -f options. "Usage Note" for the file types that file command does not attempt to classify.
–M magic
Uses the file magic to classify the file type. No default position-sensitive tests, default context-sensitive tests, nor AMODE tests shall be applied, unless the -d option is also specified. See the usage notes for more information.
–m magic
Alters the classification of regular files when examining the file content.
If the variable _UNIX03=YES is set
Then file attempts to classify the file type using the following tests, in order:
  1. Using the file magic.
  2. Using the default position-sensitive tests (/etc/magic ).
  3. Using the default context-sensitive tests built into the file command.
If the variable _UNIX03 is unset or is not set to YES
Then file attempts to classify the file type using the following tests, in order:
  1. Using the file magic rather than /etc/magic.
  2. Using the default context-sensitive built into the file command.
-W option[,option]...
Specifies z/OS-specific options. The option keywords are case-sensitive. Possible options are:
filecodeset=codeset
Performs text conversion from one code set to another when reading from the file. The coded character set of the file is codeset. codeset can be a code set name known to the system or a numeric coded character set identifier (CCSID). Note that the command iconv -l lists existing CCSIDs along with their corresponding code set names. The filecodeset and pgmcodeset options can be used on files with any file tag.

If pgmcodeset is specified but filecodeset is omitted, then the default file code set is ISO8859-1 even if the file is tagged with a different code set. If neither filecodeset nor pgmcodeset is specified, text conversion will not occur unless automatic conversion is enabled or the _TEXT_CONV environment variable indicates text conversion. For more information about text conversion, see Controlling text conversion for z/OS UNIX shell commands.

If filecodeset or pgmcodeset is specified, then automatic conversion is disabled for this command invocation and the -B option is ignored if it is also specified. See z/OS UNIX System Services Planning for more information about automatic conversion.

When specifying values for filecodeset, use the values that Unicode Service supports. For more information about supported code sets, see z/OS Unicode Services User's Guide and Reference.

pgmcodeset=codeset
Performs text conversion from one code set to another when reading from the file. The coded character set of the program (command) is codeset. codeset can be a code set name known to the system or a numeric coded character set identifier (CCSID). Note that the command iconv -l lists existing CCSIDs along with their corresponding code set names. The filecodeset and pgmcodeset options can be used on files with any file tag.

If filecodeset is specified but pgmcodeset is omitted, then the default program code set is IBM-1047. If neither filecodeset nor pgmcodeset is specified, text conversion will not occur unless automatic conversion is enabled or the _TEXT_CONV environment variable indicates text conversion. For more information about text conversion, see Controlling text conversion for z/OS UNIX shell commands.

If filecodeset or pgmcodeset is specified, then automatic conversion is disabled for this command invocation and the -B option is ignored if it is also specified. See z/OS UNIX System Services Planning for more information about automatic conversion.

Restriction: The only supported values for pgmcodeset are IBM-1047 and 1047.

Examples

  1. To display the type of a file: 
    file myFile
  2. To display the type of a file, without attempting to classify regular files: 
    file -i myFile
  3. To display the type of a text file containing UTF-8 characters, assuming that:
    • The text file is untagged and you do not want to tag it or enable automatic conversion, and
    • You cannot alter the tag (for example, you are checking an untagged public text file or a read-only text file)
    file -W filecodeset=UTF-8,pgmcodeset=IBM-1047 myUtf8File
  4. To display the type of a text file containing EBCDIC characters, assuming that automatic conversion has been enabled but the text file is incorrectly tagged as ASCII: 
    file -B myMisTaggedFile

Localization

file uses the following localization environment variables:
  • LANG
  • LC_ALL
  • LC_MESSAGES
  • LC_SYNTAX
  • NLSPATH

See Localization for more information.

Environment variables

file uses the following environment variables:
_UNIX03
See Shell commands changed for UNIX03 for more information about the effect of the _UNIX03 environment variable on this command.
_TEXT_CONV
Contains text conversion information for the command. The text conversion information is not used when either the -B option or the filecodeset or pgmcodeset option (-W option) is specified. For more information about text conversion, see Controlling text conversion for z/OS UNIX shell commands.

Files

file uses the following file:
/etc/magic
Default system magic file.

For file to work, you need to copy the magic file from the /samples directory to the /etc directory.

For more information about enabling file, see the section on copying configuration files in z/OS UNIX System Services Planning. Additional information about the magic file can be found in magic — Format of the /etc/magic file.

Usage notes

  1. LC_SYNTAX only affects the interpretation of the input file that did not match any magic file template. It does not affect the interpretation of the magic file.

    Because of this, an input file that contains characters from a code page other than IBM-1047 cannot match the magic file, which contains IBM-1047 characters. If you need to match character in different code pages, you can use the -m or -M option to specify a magic file created with the desired code page.

  2. The tests applying to a file when running the command follow the rules outlined in Table 1.
    Table 1. Rules for testing files
    If the following options are specified... Then the position-sensitive tests are applied in the following sequence... Default context-sensitive tests applied?
    None AMODE > /etc/magic Yes
    -d AMODE > /etc/magic Yes
    -M MAGIC MAGIC No
    -m magic
    • If the variable _UNIX03=YES is set,
      • magic > AMODE > /etc/magic
    • If the variable _UNIX03 is unset or is not set to YES,
      • AMODE > magic
    		 Yes
    -d -M MAGIC AMODE > /etc/magic > MAGIC Yes
    -M MAGIC -d MAGIC > AMODE > /etc/magic Yes
    -d -m magic AMODE > /etc/magic > magic Yes
    -m magic -d magic > AMODE > /etc/magic Yes
    -M MAGIC -m magic MAGIC > magic No
    -m magic -M MAGIC magic > MAGIC No
    -d -M MAGIC -m magic AMODE > /etc/magic > MAGIC > magic Yes
    -d -m magic -M MAGIC AMODE > /etc/magic > magic > MAGIC Yes
    -M MAGIC -d -m magic MAGIC > AMODE > /etc/magic > magic Yes
    -M MAGIC -m magic -d MAGIC > magic > AMODE > /etc/magic Yes
    -m magic -d -M MAGIC magic > AMODE > /etc/magic > MAGIC Yes
    -m magic -M MAGIC -d magic > MAGIC > AMODE > /etc/magic Yes
    Note:
    1. The first column specifies the appearance of the -d, -M and -m options in the command line.
    2. The second column gives what position-sensitive tests are applied and in what sequence, given the options specified in the first column:
      • AMODE is a default position-sensitive system test which is only used on an executable file to determine the addressing mode.
      • "/etc/magic" means the default position-sensitive tests in /etc/magic.
      • "MAGIC" means the position-sensitive tests in the magic file specified by "-M".
      • "magic" means the position-sensitive tests in the magic file specified by "-m".
      • Tests not appearing in the cell are not applied.
    3. The third column gives whether the default context-sensitive tests (built into the file command) are applied, given the options specified in the first column.
  3. If -d option is specified together with -E option, the AMODE tests will not be applied. If -M magic option is specified alone, the AMODE tests will not be applied.
  4. The standard output messages of the file utility will contain the specified strings, but not limited to, listed in Table 2.
    Table 2. Output messages of the file utility
    If file is: Will contain the string: See note
    Nonexistent Cannot open None
    Block special Block special a
    Character special Character special a
    Directory Directory a
    FIFO Fifo a
    Socket Socket a
    Symbolic link Symbolic link to a
    External symbolic link External link to a
    Regular file Regular file a,b
    Empty regular file Empty c
    Regular file that cannot be read Cannot open c
    Executable binary Executable d,f
    ar archive library (see ar ) Archive d,f
    Extended cpio format (see pax) cpio archive d,f
    Extended tar format (ustar in pax) tar archive d,f
    Shell script Commands text e,f
    C-language source C program text e,f
    FORTRAN source Fortran program text e,f
    Regular file whose type cannot be determined Data None
    Note:
    1. This is a file attribute test.
    2. This test is applied only if the -i option is specified.
    3. This test is applied only if the -i option is not specified.
    4. This is a default position-sensitive test.
    5. This is a default context-sensitive test.
    6. Default position-sensitive tests and default context-sensitive tests are not applied if the -M magic option is specified unless the -d option is also specified.

Exit values

0
Successful completion
1
Failure due to any of the following:
  • A missing filelist after –f
  • More than one –f option on the command line
  • Cannot find the magic file
  • Incorrect command-line option
  • Too few command-line arguments
  • Cannot access a specified file
  • Cannot open filelist
  • Cannot open the magic file
  • A format error in the magic file
  • Out of memory for reading or magic entries
  • A bad number in the magic file
  • A misplaced > in the magic file.
  • The code set is not valid
  • Could not turn off automatic conversion
  • Could not perform requested text conversion

Portability

POSIX.2 User Portability Extension, X/Open Portability Guide, UNIX systems.

All options are extensions of the POSIX standard.

The –B and -W options are extensions of the POSIX standard.

Related information

magic — Format of the /etc/magic file for more information about the magic file format.

Parent topic: Shell command descriptions