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.

         -W<Error>:
           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.

         -smp:
           Compiles using the SMP emulator. This is mainly useful for  compiling  native  code,  which  must  be
           compiled with the same runtime system that it is to be run on.

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

         -server:
           Use the compile server.

         -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 situtations 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)