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NAME

       erlc - Compiler

DESCRIPTION

       The  erlc  program  provides  a  common  way  to  run  all compilers in the Erlang system.
       Depending on the extension of each input file,  erlc  invokes  the  appropriate  compiler.
       Regardless  of which compiler is used, the same flags are used to provide parameters, such
       as include paths and output directory.

       The current working directory, ".", is not included in the  code  path  when  running  the
       compiler.  This  is  to  avoid  loading Beam files from the current working directory that
       could potentially be in conflict with the compiler or the Erlang/OTP system  used  by  the
       compiler.

EXPORTS

       erlc flags file1.ext file2.ext...

              Compiles one or more files. The files must include the extension, for example, .erl
              for Erlang source code, or .yrl for Yecc source code. Erlc uses  the  extension  to
              invoke the correct compiler.

GENERALLY USEFUL FLAGS

       The following flags are supported:

         -I <Directory>:
           Instructs the compiler to search for include files in the Directory. When encountering
           an -include or -include_lib directive, the compiler searches for header files  in  the
           following directories:

           * ".", the current working directory of the file server

           * The base name of the compiled file

           * The  directories specified using option -I; the directory specified last is searched
             first

         -o <Directory>:
           The directory where the compiler is to place the output files. Defaults to the current
           working directory.

         -D<Name>:
           Defines a macro.

         -D<Name>=<Value>:
           Defines  a macro with the specified value. The value can be any Erlang term. Depending
           on the platform, the value may need to  be  quoted  if  the  shell  itself  interprets
           certain  characters.  On Unix, terms containing tuples and lists must be quoted. Terms
           containing spaces must be quoted on all platforms.

         -WError:
           Makes all warnings into errors.

         -W<Number>:
           Sets warning level to Number. Defaults to 1. To turn off warnings, use -W0.

         -W:
           Same as -W1. Default.

         -v:
           Enables verbose output.

         -b <Output_type>:
           Specifies the type of output file. Output_type is the same as the  file  extension  of
           the output file, but without the period. This option is ignored by compilers that have
           a single output format.

         -no-server:
           Do not use the compile server.

         -server:
           Use the compile server.

         -enable-feature <Feature>:
           Enables the feature feature during compilation. The special feature all can be used to
           enable all features.

         -disable-feature <feature>:
           Disables  the  feature feature during compilation. The special feature all can be used
           to disable all non permanent features.

         -list-features:
           List short  descriptions  of  the  current  configurable  features.  Non  configurable
           features, i.e., those with a status of rejected or permanent will not be shown.

         -describe-feature <feature>:
           Show long description and history of feature feature.

         -M:
           Produces  a Makefile rule to track header dependencies. The rule is sent to stdout. No
           object file is produced.

         -MMD:
           Generate dependencies as a side-effect. The object file will be  produced  as  normal.
           This option overrides the option -M.

         -MF <Makefile>:
           As  option  -M,  except  that  the  Makefile is written to Makefile. No object file is
           produced.

         -MD:
           Same as -M -MF <File>.Pbeam.

         -MT <Target>:
           In conjunction with option -M or -MF, changes the name of the rule emitted to Target.

         -MQ <Target>:
           As option -MT, except that characters special to make/1 are quoted.

         -MP:
           In conjunction with option -M or -MF, adds a phony target for each dependency.

         -MG:
           In conjunction with option -M or -MF, considers missing headers as generated files and
           adds them to the dependencies.

         --:
           Signals  that  no  more  options  will follow. The rest of the arguments is treated as
           filenames, even if they start with hyphens.

         +<Term>:
           A flag starting with a plus (+) rather than a hyphen is converted to  an  Erlang  term
           and  passed  unchanged  to the compiler. For example, option export_all for the Erlang
           compiler can be specified as follows:

         erlc +export_all file.erl

           Depending on the platform, the value may  need  to  be  quoted  if  the  shell  itself
           interprets  certain  characters.  On  Unix,  terms containing tuples and lists must be
           quoted. Terms containing spaces must be quoted on all platforms.

SPECIAL FLAGS

       The following flags are useful in special situations, such as rebuilding the OTP system:

         -pa <Directory>:
           Appends Directory to the front of the code path in the invoked Erlang  emulator.  This
           can be used to invoke another compiler than the default one.

         -pz <Directory>:
           Appends Directory to the code path in the invoked Erlang emulator.

SUPPORTED COMPILERS

       The following compilers are supported:

         .erl:
           Erlang source code. It generates a .beam file.

           Options  -P,  -E, and -S are equivalent to +'P', +'E', and +'S', except that it is not
           necessary to include the single quotes to protect them from the shell.

           Supported options: -I, -o, -D, -v, -W, -b.

         .S:
           Erlang assembler source code. It generates a .beam file.

           Supported options: same as for .erl.

         .core:
           Erlang core source code. It generates a .beam file.

           Supported options: same as for .erl.

         .yrl:
           Yecc source code. It generates an .erl file.

           Use option -I with the name of a file to use that file as a customized  prologue  file
           (option includefile).

           Supported options: -o, -v, -I, -W.

         .mib:
           MIB for SNMP. It generates a .bin file.

           Supported options: -I, -o, -W.

         .bin:
           A compiled MIB for SNMP. It generates a .hrl file.

           Supported options: -o, -v.

         .rel:
           Script file. It generates a boot file.

           Use  option -I to name directories to be searched for application files (equivalent to
           the path in the option list for systools:make_script/2).

           Supported option: -o.

         .asn1:
           ASN1 file. It creates an .erl, .hrl,  and  .asn1db  file  from  an  .asn1  file.  Also
           compiles the .erl using the Erlang compiler unless option +noobj is specified.

           Supported options: -I, -o, -b, -W.

         .idl:
           IC file. It runs the IDL compiler.

           Supported options: -I, -o.

COMPILE SERVER

       The compile server can be used to potentially speed up the build of multi-file projects by
       avoiding to start an Erlang system for each file to compile. Whether it will speed up  the
       build depends on the nature of the project and the build machine.

       By  default,  the  compile server is not used. It can be enabled by giving erlc the option
       -server or by setting the environment variable ERLC_USE_SERVER to yes or true.

       When the compile server is enabled, erlc will  automatically  use  the  server  if  it  is
       started  and start the server if has not already started. The server will terminate itself
       when it has been idle for some number of seconds.

       erlc and the compile server communicate using the Erlang distribution. The compile  server
       is  started  as a hidden node, with a name that includes the current user. Thus, each user
       on a computer has their own compile server.

       Using the compile server does not always  speed  up  the  build,  as  the  compile  server
       sometimes  must  be  restarted to ensure correctness. Here are some examples of situations
       that force a restart:

         * erlc wants to use a different version of Erlang than the compile server is using.

         * erlc wants to use different options for erl than the compile server was started  with.
           (A  change to code path using the option -pa could cause different parse transforms to
           be loaded. To be safe, the compile server will be restarted when  any  erl  option  is
           changed.)

         * If  the  current  working  directory  for erlc is different from the working directory
           active when the compile server was started, and  if  the  compile  server  has  active
           jobs,  it  will  be restarted as soon as those jobs have finished. (Build systems that
           build files randomly across multiple directories in parallel will probably not benefit
           from the compile server.)

ENVIRONMENT VARIABLES

         ERLC_EMULATOR:
           The  command  for  starting the emulator. Defaults to erl in the same directory as the
           erlc program itself, or, if it does not exist, erl in any of the directories specified
           in environment variable PATH.

         ERLC_USE_SERVER:
           Allowed  values  are yes or true to use the compile server, and no or false to not use
           the compile server. If other values are given, erlc will print a warning  message  and
           continue.

         ERLC_SERVER_ID:
           Tells erlc to identify the compile server by the given name, allowing a single user to
           run multiple unrelated builds in parallel without them affecting each other, which can
           be  useful  for shared build machines and the like. The name must be alphanumeric, and
           it defaults to being empty.

SEE ALSO

       erl(1), compile(3erl), yecc(3erl), snmp(3erl)