Getting Information About Files and Directories

To see file type, size in bytes, date modified, owners , and permissions:

• ls -l path
  
  Use the -l option to the ls command ( -l for long form ).
  
  ls -l /
  
  shows you a long-form listing of your root directory ( Figure 5.21 ).
  
  

  Figure 5.21. Using ls -l to get information about files. (Your output may differ .)

  localhost:~ vanilla$
  
  ls -l /
  
  total 9642
  drwxrwxr-x           30 root         admin           1020 Mar 26 09:29 Applications
  -rw-r--r--            1 root         admin           3584 Mar 26 09:58 Desktop DB
  -rw-r--r--            1 root         admin           2 Jan 14 18:48 Desktop DF
  drwxrwxr-x           13 root         admin           442 Jan 17 14:38 Developer
  drwxrwxr-t           43 root         admin           1462 Mar 26 09:29 Library
  drwxr-xr-x            1 root         wheel           512 Mar 26 10:10 Network
  drwxr-xr-x            4 root         wheel           136 Mar 26 09:26 System
  drwxrwxr-t            8 root         admin           272 Mar 26 09:26 Users
  drwxrwxrwt            4 root         admin           136 Mar 26 10:10 Volumes
  drwxr-xr-x            4 root         admin           136 Jan 14 18:20 automount
  drwxr-xr-x           40 root         wheel           1360 Mar 26 09:20 bin
  drwxrwxr-t            2 root         admin           68 Nov 14 02:31 cores
  dr-xr-xr-x            2 root         wheel           512 Mar 26 10:09 dev
  lrwxr-xr-x            1 root         admin           11 Mar 26 09:20 etc -> private/etc
  lrwxr-xr-x            1 root         admin           9 Mar 26 10:09 mach -> /mach.sym
  -r-r--r--            1 root         admin           597876 Mar 26 10:09 mach.sym
  -rw--r--r--           1 root         wheel           4312948 Mar 19 19:56 mach_kernel
  drwxr-xr-x            6 root         wheel           204 Mar 26 10:09 private
  drwxr-xr-x           63 root         wheel           2142 Mar 26 09:26 sbin
  lrwxr-xr-x            1 root         admin           11 Mar 26 09:22 tmp -> private/tmp
  drwxr-xr-x           11 root         wheel           374 Jan 17 14:29 usr
  lrwxr-xr-x            1 root         admin           11 Mar 26 09:23 var -> private/var
  localhost:~ vanilla$
  

  
  Figure 5.22 shows what the different parts of the output mean.
  
  

  Figure 5.22. This diagram shows what the output of ls -l means.

  

  
  

To show file sizes in kilobytes:

• Use the -s and -k options together:
  
  ls -sk path
  
  The -s option means "List sizes," and the -k option means "List sizes in kilobytes." If you omit the k option, the size is listed in blocks, which vary in size depending on the version of Unix and how the disk was formatted. On our disk in Mac OS X, each block is .5 Kbyte.
  
  

Displaying file metadata

The mdls command lists the metadata associated with a file but is only available in the Darwin/Mac OS X version of Unix. It was introduced in Mac OS X 10.4 (along with the mdfind command, covered in Chapter 4). See the "Searching for Files" section of Chapter 4 for more details about metadata; briefly , the metadata displayed by mdls is the same metadata that the Spotlight feature of Mac OS X searches. For more on Spotlight see "Working with Spotlight" (http://developer.apple.com/macosx/spotlight.html).

To list the metadata attributes of a file:

• mdls path
  
  This displays the metadata associated with the file or directory whose path you supplied. For example:
  
  

  mdls /Developer/Examples/Dashboard/
  
  Documentation/DashboardTutorial.pdf
  

  
  Figure 5.23 shows this.
  
  

  Figure 5.23. Displaying a file's metadata using the mdls command.

  localhost:~ vanilla$
  
  mdls /Developer/Examples/Dashboard/Documentation/DashboardTutorial.pdf
  
  /Developer/Examples/Dashboard/Documentation/DashboardTutorial.pdf -
  kMDItemAttributeChangeDate               = 2005-04-14 13:19:33 -0700
  kMDItemAuthors                           = ("Apple Computer, Inc.")
  kMDItemContentCreationDate               = 2004-06-16 23:38:06 -0700
  kMDItemContentModificationDate           = 2004-06-16 23:38:06 -0700
  kMDItemContentType                       = "com.adobe.pdf"
  kMDItemContentTypeTree                             = (
            "com.adobe.pdf",
            "public.data",
            "public.item",
            "public.composite-content",
            "public.content"
  )
  kMDItemCreator                          = "XEP 3.7.8 Client"
  kMDItemDisplayName                      = "DashboardTutorial.pdf"
  kMDItemEncodingApplications             = ("XEP PDF Generator \U2013 RenderX, Inc.")
  kMDItemFSContentChangeDate              = 2004-06-16 23:38:06 -0700
  kMDItemFSCreationDate                   = 2004-06-16 23:38:06 -0700
  kMDItemFSCreatorCode                    = 0
  kMDItemFSFinderFlags                    = 0
  kMDItemFSInvisible                      = 0
  kMDItemFSLabel                          = 0
  kMDItemFSName                           = "DashboardTutorial.pdf"
  kMDItemFSNodeCount                      = 0
  kMDItemFSOwnerGroupID                   = 80
  kMDItemFSOwnerUserID                    = 0
  kMDItemFSSize                           = 346134
  kMDItemFSTypeCode                       = 0
  kMDItemID                               = 661176
  kMDItemKind                             = "PDF Document"
  kMDItemLastUsedDate                     = 2004-06-16 23:38:06 -0700
  kMDItemNumberOfPages                    = 40
  kMDItemPageHeight                       = 792
  kMDItemPageWidth                        = 612
  kMDItemSecurityMethod                   = "None"
  kMDItemTitle                            = "Dashboard Tutorial"
  kMDItemUsedDates                        = (2004-06-16 23:38:06 -0700)
  kMDItemVersion                          = "1.3"
  localhost:~ vanilla$
  

  
  

Tips

• You can restrict the output of mdls to a single metadata attribute using the -name optionfor example:

  mdls -name kMDItemTitle
  
  Documents/Unix-VQP-05.doc
  

  
  

• We provide a partial list of metadata attributes in Table 4.3 in Chapter 4, and a longer list is available in "Introduction to Spotlight Metadata Attributes Reference" (http://developer.apple.com/documentation/Carbon/Reference/MetadataAttributesRef).

Discerning different types of files

Not all files are the same. For example, some files are directories, while others are special files the operating system uses to interact with disks and other devices.

Even among regular files there are differences. For example, some files are images, others consist of programming source code in various languages, and some are compiled applications. Among files created with Mac Classic applications, there are attributes such as stationery (if a Mac file is marked as stationery, then it is a sort of templatea read-only document you use as a starting place for creating new documents) and creator .

There are several ways to find out a file's type, each showing different kinds of information.

To see file types using ls -l:

• Examine the output from ls -l .
  
  The first character of each line tells you what kind of file it is. Table 5.4 summarizes the meaning of the first character in the output.
  
  

  Table 5.4. File Types from ls -l

  F IRST C HARACTER	M EANING
  -	Regular file.
  d	Directory.
  l	Symbolic link. A special kind of file that contains the path of another file, similar to a Mac alias.
  b	Block special files represent physical devices that deal with blocks of data, such as disks (or drives ).
  c	Character special files represent devices that deal with streams of characters , such as modems.
  s	Socket links (also called named pipes ) are special files that connect to programs. Writing data to the file actually "pipes" the data to the program.

  
  
• If you want information about a directory, then add the -d option:
  
  ls -ld directorypath
  
  The ls command reports information about the directory file itself, not its contents.
  
  

To see basic Unix file-type information:

• Use the -F option to ls :
  
  ls -F path
  
  The -F (for file type ) option distinguishes directories, executable files (Unix commands), and symbolic links by adding / after directories, @ after symbolic links, and * after executables. Figure 5.24 compares ls / with ls -F / .
  
  

  Figure 5.24. The -F option to ls adds characters to some filenames showing file type. (Your output may differ.)

  localhost:~ vanilla$
  
  ls /
  
  Applications          Network          bin          mach.sym           usr
  Desktop DB            System           cores        mach_kernel        var
  Desktop DF            Users            dev          private
  Developer             Volumes          etc          sbin
  Library               automount        mach         tmp
  g4-cube:~ vanilla$
  
  ls -F /
  
  Applications/         Network/         bin/          mach.sym          usr/
  Desktop DB            System/          cores/        mach_kernel       var@
  Desktop DF            Users/           dev/          private/
  Developer/            Volumes/         etc@          sbin/
  Library/              automount/       mach@         tmp@
  localhost:~ vanilla$
  

  
  

To guess file types from hundreds of possibilities:

• file path
  
  The file command attempts to figure out what kind of file each argument is. It uses a set of tests defined in the /usr/share/file/magic file. The file command can recognize more than 100 file types, but it is not 100 percent accurate. Some of the file types that file will try to recognize are image formats (such as JPEG, GIF, and PNG), programming languages (C, Perl, and Java), and compressed file formats (StuffIt archives, ZIP files, and Unix compress format).
  
  As with most commands that deal with filenames, you can supply as many paths as you like.
  
  file /etc/*
  
  applies the file command to everything in the /etc directory.
  
  Most of the files in the /etc directory are text files, but the file command is able to look inside them and make an educated guess about what kind of text file each one is ( Figure 5.25 ).
  
  

  Figure 5.25. The file command attempts to figure out what kinds of files are in the directory. (Again, your output may differ.)

  localhost:~ vanilla$
  
  file /etc/*
  
  /etc/6to4.conf:                      ASCII text
  /etc/6to4.conf.applesaved:           ASCII text
  /etc/6to4.conf.applesaved2:          ASCII text
  /etc/6to4.conf.applesaved3:          ASCII text
  /etc/X11:                            directory
  /etc/afpovertcp.cfg:                 ASCII English text
  /etc/aliases:                        symbolic link to `postfix/aliases'
  /etc/aliases.db:                     Berkeley DB 1.85 (Hash, version 2, native byte-order)
  /etc/appletalk.cfg:                  ASCII text
  /etc/appletalk.nvram.en0:            data
  /etc/authorization:                  XML document text
  /etc/authorization.cac:              XML document text
  /etc/bashrc:                         ASCII text
  /etc/crontab:                        ASCII English text
  
  (Partial output)
  

  
  

Working with Classic Mac metadata

In Mac OS X 10.4 a new system of storing file metadata was introduced (see "Displaying file metadata" earlier in this chapter, and " mdfind " in Chapter 4); because of this we will refer to the kind of metadata used in the Mac OS prior to Mac OS X as Classic Mac metadata .

The challenges of integrating preMac OS X files with a Unix system are numerous and difficult. Apple has done quite an amazing job of providing backward compatibility for files created with older applications, while allowing thousands of Unix tools to operate . Still, there are some issues a command-line user should be aware of. (An excellent paper on some of the technical problems Apple has had to deal with is available online at USENIX 2000; www.wsanchez.net/papers/USENIX_2000/.)

Traditional Mac applications, and some Mac OS X applications, use an older system of storing information about each file that standard Unix commands do not understand. For example, the Finder can mark a file as "locked," and Unix command-line programs will not be able to alter the file, but neither will they tell you why you can't change themyou'll just get an error when trying to delete or rename a locked file.

(You can use the Darwin/Mac OS X version of the ls command with the -lo options:

ls -lo filename

to show if a file is "locked": the notation uchg [ unchangeable ] is added to the output for locked files.)

The GetFileInfo command (provided as part of the Mac OS X Developer Tools collection) will show you this Mac-specific information.

To see the Mac metadata for a file:

• /Developer/Tools/GetFileInfo path
  
  For example,
  
  

  /Developer/Tools/GetFileInfo
  
  /usr/share/doc/bash/bash.pdf
  

  
  is shown in Figure 5.26 .
  
  

  Figure 5.26. The GetFileInfo command reveals Mac-specific metadata.

  localhost:~ vanilla$
  
  /Developer/Tools/GetFileInfo /usr/share/doc/bash/bash.pdf
  
  file: "/usr/share/doc/bash/bash.pdf"
  type: ""
  creator: ""
  attributes: avbstclinmedz
  created: 03/13/2005 14:31:45
  modified: 03/13/2005 14:31:45
  localhost:~ vanilla$
  

  
  The attributes line lists a series of file attributes. Each letter represents one attribute that is either On (uppercase) or off (lowercase). See Table 5.5 for the meaning of each attribute.
  
  

  Table 5.5. File Attributes from GetFileInfo

  O PTION /A TTRIBUTE	M EANING
  a or A	Alias file
  v or V	Invisible [*]
  b or B	Bundle
  s or S	System (name locked)
  t or T	Stationery
  c or C	Custom icon [*]
  l or L	Locked
  i or I	Inited [*]
  n or N	No INIT resources
  m or M	Shared (can run multiple times)
  e or E	Hidden extension [*]
  d or D	Desktop [*]

  
  

  ^[*] Note: Uppercase means on, lowercase means off. Options and attributes with * are allowed with folders.

  Unlike many other Unix commands, GetFileInfo does not handle multiple filenames as arguments.
  
  GetFileInfo is installed in a directory where your shell will not normally find it, so when you use the command, you must use its full path:
  
  /Developer/Tools/GetFileInfo
  
  For instructions on how to configure your shell to look in more places for commands, see Chapter 7.
  
  

Tip

• If a file is locked, you can unlock it from the command line using the SetFile command, described below. See also the chflags command ( man chflags ).