ARCH(1)                      General Commands Manual                     ARCH(1)

     arch – print architecture type or run selected architecture of a universal

     arch [-32] [-64] [[-arch_name | -arch arch_name]...] [-c] [-d envname]...
          [-e envname=value]... [-h] prog [args ...]

     The arch command with no arguments, displays the machine's architecture

     The other use of the arch command is to run a selected architecture of a
     universal binary.  A universal binary contains code that can run on
     different architectures.  By default, the operating system will select the
     architecture that most closely matches the processor type.  A 64-bit
     architecture is preferred over a 32-bit architecture on a 64-bit processor,
     while only 32-bit architectures can run on a 32-bit processor.

     When the most natural architecture is unavailable, the operating system
     will try to pick another architecture.  On 64-bit processors, a 32-bit
     architecture is tried.  Otherwise, no architecture is run, and an error

     The arch command can be used to alter the operating system's normal
     selection order.  The most common use is to select the 32-bit architecture
     on a 64-bit processor, even if a 64-bit architecture is available.

     The arch_name argument must be one of the currently supported

           i386     32-bit intel

           x86_64   64-bit intel

           x86_64h  64-bit intel (haswell)

           arm64    64-bit arm

           arm64e   64-bit arm (Apple Silicon)

     If the binary does not contain code for arch_name, the arch command may try
     to select a close match.  If arm64 is specified and not found, arm64e will
     be tried next.  If this happens, the order the architectures will be tried
     is not guaranteed.

     Either prefix the architecture with a hyphen, or (for compatibility with
     other commands), use -arch followed by the architecture.

     If more than one architecture is specified, the operating system will try
     each one in order, skipping an architecture that is not supported on the
     current processor, or is unavailable in the universal binary.

     The other options are:

     -32                     Add the native 32-bit architecture to the list of

     -64                     Add the native 64-bit architecture to the list of

     -c                      Clears the environment that will be passed to the
                             command to be run.

     -d envname              Deletes the named environment variable from the
                             environment that will be passed to the command to
                             be run.

     -e envname=value        Assigns the given value to the named environment
                             variable in the environment that will be passed to
                             the command to be run.  Any existing environment
                             variable with the same name will be replaced.

     -h                      Prints a usage message and exits.

     The prog argument is the command to run, followed by any arguments to pass
     to the command.  It can be a full or partial path, while a lone name will
     be looked up in the user's command search path.

     If no architectures are specified on the command line, the arch command
     takes the basename of the prog argument and searches for the first property
     list file with that basename and the .plist suffix, in the archSettings
     sub-directory in each of the standard domains, in the following order:

           ~/Library/archSettings             User settings

           /Library/archSettings              Local settings

           /Network/Library/archSettings      Network settings

           /System/Library/archSettings       System settings

     This property list contains the architecture order preferences, as well as
     the full path to the real executable.  Please refer to the EXAMPLES section
     for an example of the property list file format.

   Making links to the arch command
     When a link is made to arch command with a different name, that name is
     used to find the corresponding property list file.  Thus, other commands
     can be wrapped so that they have custom architecture selection order.

     Because of some internal logic in the code, hard links to the arch command
     may not work quite right.  It is best to avoid using hard links, and only
     use symbolic links to the arch command.

     The environment variable ARCHPREFERENCE can be used to provide architecture
     order preferences.  It is checked before looking for the corresponding
     property list file.

     The value of the environment variable ARCHPREFERENCE is composed of one or
     more specifiers, separated by semicolons.  A specifier is made up of one,
     two or three fields, separated by colons.  Architectures specified in
     order, are separated by commas and make up the last (mandatory) field.  The
     first field, if specified, is a name of a program, which selects this
     specifier if that name matches the program name in question.  If the name
     field is empty or there is no name field, the specifier matches any program
     name.  Thus, ordering of specifiers is important, and the one with no name
     should be last.

     When the arch command is called directly, the prog name provides the path
     information to the executable (possibly via the command search path).  When
     a name is specified in a ARCHPREFERENCE specifier, the path information can
     alternately be specified as a second field following the name.  When the
     arch command is called indirectly via a link, this path information must be
     specified.  If not specified as a second field in a specifier, the
     executable path will be looked up in the corresponding property list file.

   archSettings Property List Format
     This is an example of a property list file as is expected in one of the
     archSettings locations mentioned above:

           <?xml version="1.0" encoding="UTF-8"?>
           <!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "">
           <plist version="1.0">

           A specifier that matches any name.

           A specifier that matches the program named foo (the full executable
           path is in the foo.plist file).

           A specifier with all fields specified.

           A specifier for baz and a second specifier that would match any other


     Running the arch command on an interpreter script may not work if the
     interpreter is a link to the arch command.

macOS 12.1                      February 15, 2021                     macOS 12.1