The ASN1C compiler distribution contains command-line compiler executables as well as a graphical user interface (GUI) wizard that can aid in the specification of compiler options. This section describes how to run the command-line version; the next section describes the GUI.

To test if the compiler was successfully installed, enter asn1c with no parameters as follows (note: if you have not updated your PATH variable, you will need to enter the full pathname):

       asn1c

You should observe the following display (or something similar):

ASN1C Compiler, Version 7.7.x
Copyright (c) 1997-2023 Objective Systems, Inc. All Rights Reserved.

Licensed Copy. Registered To: Objective Systems

Usage: asn1c <filename> <options>

    <filename>          ASN.1 or XSD source filename(s).  Multiple filenames
                          may be specified.  * and ? wildcards are allowed.
                        can also be an ASN1C GUI .acproj file.

  language options:
    -c                  generate C code
    -c++                generate C++ code
    -c++11              generate C++ code that uses C++11 features
    -c#                 generate C# code
    -java               generate Java code
    -cldc               generate Java ME CLDC compatible code
    -python             generate Python code
    -go                 generate Go language code

  encoding rule options:
    -ber                generate BER encode/decode functions
    -cer                generate CER encode/decode functions
    -der                generate DER encode/decode functions
    -oer                generate OER encode/decode functions
    -coer               generate canonical OER encode/decode functions
    -mder               generate MDER encode/decode functions
    -per                generate PER encode/decode functions
    -aper               generate aligned PER encode/decode functions
    -uper               generate unaligned PER encode/decode functions
    -xer                generate XER encode/decode functions
    -xml                generate XML encode/decode functions
    -xsd [<filename>]   generate XML schema for XML/XER\n"
    -json | -jer        generate JSON encode/decode functions
    -jer+               generate JSON encode/decode functions with ObjSys
                          extensions
    -avn                generate ASN.1 Value Notation encode/decode functions
                           (currently C/C++ only)
    -3gl3               generate 3GPP layer 3 encode/decode functions

  basic options:
    -asn1 [<file>]      generate pretty-printed ASN.1 source code
    -asnstd <std>       set standard to be used for parsing ASN.1
                        source file. Possible values - x208, mixed, x680,
                        x680-2021, x680-2015, x680-2008 (default is x680)
    -client             generate sample socket writer client program
    -compact            generate compact code
    -compat <version>   generate code compatible with previous
                        compiler version. <version> format is
                        x.x (for example, 5.3)
    -config <file>      specify configuration file
    -depends            compile main file and dependent IMPORT items
    -events             generate code to invoke SAX-like event handlers
    -raw-events         generate code to invoke raw event handlers, designed
                        to minimize decoding operations, compared to -events
                        (C/C++ and PER only)
    -gen-from-template <file> generate a program from a template
    -genjrtkey          generate Java _Rtkey.java runtime license
    -genlic [<filename>] generate runtime license file
    -genTest [<filename>] generate sample test functions
    -html               generate HTML marked-up version of ASN.1
    -I <directory>      set import file directory
    -lax                do not generate constraint checks in code
    -laxsyntax          do not do a thorough ASN.1 syntax check
    -list               generate listing
    -allow-ambig-tags   allow ambiguous tags in input specifications
    -noaccomment        do not generate the asn1c command line comment
    -noContaining       do not generate inline type for CONTAINING <type>
    -nodatestamp        do not put date/time stamp in generated files
    -nodecode           do not generate decode functions
    -noencode           do not generate encode functions
    -noIndefLen         do not generate indefinite length tests
    -noObjectTypes      do not gen types for items embedded in info objects
    -noOpenExt          do not generate open extension elements
    -noPLMN             disable special treatment of PLMNidentity (e.g., from the RANAP specs)
    -noTBCD, -noBCD     disable special treatment of BCD and TBCD strings
    -notypes            do not generate type definitions
    -noxmlns            do not generate XML namespaces for ASN.1 modules
    -o <directory>      set output file directory (also '-srcdir <dir>')
    -libdir <directory> set output libraries directory
    -bindir <directory> set output binary directory
    -objdir <directory> set output object directory
    -prjdir <directory> set the output project directory; this automatically
                           sets sane defaults for the library directory
                           (lib), binary directory (bin), source directory
                           (src), and object directory (obj)
    -proj <file>        incorporate the contents of an ASN1C GUI project file
    -param <name>=<value> create types from param types using given value
    -pdu <type>         designate <type> to be a Protocol Data Unit (PDU)
                        (<type> may be "all" to select all type definitions)
    -usepdu <type>      specify a Protocol Data Unit (PDU) type for which
                        sample reader/writer programs and test code has to
                        be generated
    -print [<filename>] generate print functions
    -prtfmt details | bracetext  format of output generated by print
    -randtest [<filename>] generate run-time random test functions
    -shortnames         reduce the length of compiler generated names
    -strict             strict standards conformance and constraint checking
    -syntaxcheck        do syntax check only (no code generation)
    -reader             generate sample reader program
    -server             generate sample socket reader server program
    -trace              add trace diag msgs to generated code
    -[no]UniqueNames    resolve name clashes by generating unique names
                          For C/C++, default=on; use -noUniqueNames to disable
    -warnings           output compiler warning messages
    -writer             generate sample writer program

  C/C++ code generation options:
    -array              use arrays for SEQUENCE OF/SET OF types
    -arraySize <size>   specify the size of the array variable
    -compare [<filename>] generate comparison functions
    -copy [<filename>]  generate copy functions
    -cppNs <namespace>  add a C++ namespace to generated code (C++ only)
    -default-int-type <value>   specify the default integer type for
                          unconstrained integers: {int8, uint8, int16,
                          uint16, int32, uint32, int64, uint64, string}
    -dynamic            use dynamic memory for strings and arrays
    -dynamicArray       use dynamic arrays for SEQUENCE OF/SET OF types
    -linkedList         use linked-lists for SEQUENCE OF/SET OF types
    -hfile <filename>   C or C++ header (.h) filename
                          (default is <ASN.1 Module Name>.h)
    -cfile <filename>   C or C++ source (.c or .cpp) filename
                          (default is <ASN.1 Module Name>.c)
    -genBitMacros       generate named bit set, clear, test macros
    -genFree            generate memory free functions for all types
    -nofree             for C++ do not generate destructors
    -hdrGuardPfx <pfx>  add prefix to header guard #defines in .h files
    -maxcfiles          generate separate file for each function
    -maxlines <num>     set limit of number of lines per source file
                        (default value is 50000)
    -noBitStr32         do not use BitStr32 type for small bit strings
    -noEnumConvert      do not generate conversion functions for enumerated
                           items (BER/CER/DER/PER only)
    -noInit             do not generate initialization functions
    -oh <directory>     set output directory for header files
    -oid-as-string      use C string for object identifier
    -perIndef           add support for PER indefinite (fragmented) lengths
    -perPadBitStrings   pad bit strings that contain other types to octet
                           boundary
    -prtToStrm [<filename>] generate print-to-stream functions
    -hexStrFmt <hexAsciiDump | formattedHexDump | hexstring>
                        change the output format for hexadecimal strings
                        from the default (hexAsciiDump) to remove ASCII
                        output (formattedHexDump) or to use a single line
                        (hexstring)
    -static             generate static elements (not pointers)
    -stream             generate stream-based encode/decode functions
    -strict-size        strictly interpret size constraints
    -table-unions       generate union structures for table constraints
    -use-enum-types     use generated enum types in code instead of integers
    -x64                generate code for 64-bit architectures

  C/C++ makefile/project options:
    -genMake [<filename>] generate makefile to compile generated code
    -genMakeDLL [<filename>] generate makefile to build DLL
    -genMakeLib [<filename>] generate makefile to build static library
    -make [<filename>]  same as -genMake as described above.
    -maketype spaceopt|timeopt|debug  Type of makefile to generate.
    -vcproj [<version>] generate Visual Studio project files.
                          <version> is 2022, 2019 (default), 2017, 2015, 2013,
                          2012, 2010, 2008, 2005, 2003, vc6 (Windows only).
    -builddll           generate makefile/project to build DLL
    -dll, -usedll       generate makefile/project to use DLL's
    -mt                 generate makefile/project to use multithreaded libs
    -w32                generate VS nmake file for Windows 32-bit O/S
    -w64                generate VS nmake file for Windows 64-bit O/S

  Java options:
    -compare           generate equals and hashcode methods
    -copy              generate clone methods
    -dirs              output Java code to module name dirs
    -genbuild          generate build script
    -genant            generate ant build.xml script
    -genmaven          generate Maven pom.xml
    -gengradle         generate Gradle build.gradle
    -genjsources       generate <modulename>.mk for list of java files
    -getset            generate get/set methods and protected member vars
    -noevents          disable generation of event handler code.  Also
                          disables element tracking for error handling.
    -oid-as-string     use string for object identifier
    -pkgname <text>    Java package name
    -pkgpfx <text>     Java package prefix
    -tables            generate table constraint functions
    -genmetadata       generate methods for accessing ASN.1 meta data
                          like value range constraints and optional elements
    -xmlpull           generate code using XmlPull XML parser API (default)
    -stax              generate code using StAX XML parser API

  C# options:
    -compare           generate Equals and Hashcode methods
    -nspfx <text>      C# namespace prefix
    -namespace <text>  C# namespace name
    -dirs              output C# code to module name dirs
    -csfile <filename> generate one .cs file or one per module (*.cs)
    -cskeyfile <name>  have generated makefiles or Visual Studio project
                       files sign the assembly with the indicated strongly
                       named key (.snk) file
    -dotnetv5          generate .Net v5 .csproj files (if used with -vcproj)
    -dotnetv6          generate .Net v6 .csproj files (if used with -vcproj)
    -gencssources      generate <modulename>.mk for list of C# files
    -genMake           generate makefile to build generated code
    -oid-as-string     use string for object identifier
    -tables            generate table constraint functions
    -vcproj [version]  generate Visual Studio C# project files.
                          [version] is 2022, 2019 (default), 2017, 2015, 2013,
                          2012, 2010, 2008, 2005.
                          (Windows only)
    -genmetadata       generate methods for accessing ASN.1 metadata such
                          as value range constraints and optional elements
  Python options:
    -genbuild [<filename>] create build script to generate code

  Go options:
    -go-rt-inc <modules>  force inclusion of Go run-time module files
    -no-go-main        do not generate main.go file
    -oid-as-string     use string for object identifier
    -pkgname <text>    Go package name

  license options:
    -lickey <key>      set license key value
            @<file>    read license key value from file
    -licdeact          deactivate existing license
    -licinstall <file> install license file

To use the compiler, at a minimum, an ASN.1 or XSD source file must be provided. The source file specification can be a full pathname or only what is necessary to qualify the file. If directory information is not provided, the user's current default directory is assumed. If a file extension is not provided, the default extension ".asn" is appended to the name. Multiple source filenames may be specified on the command line to compile a set of files. The wildcard characters ‘*’ and ‘%’ are also allowed in source filenames (for example, the command asn1c *.asncode> will compile all ASN.1 files in the current working directory). It is also possible to provide a list of source files by adding all file specifications to a text file, one per line, and then providing the path to the text file prefixed with an '@' character.

The source file(s) must contain ASN.1 productions that define ASN.1 types and/or value specifications. This file must strictly adhere to the syntax specified in ASN.1 standard ITU-T X.680. The -asnstd x208 command-line option should be used to parse files based on the 1990 ASN.1 standard (x.208) or that contain references to ROSE macro specifications.

Specifying an ASN1C GUI project file with an extension of .acproj is also supported. In this case the information in the .acproj file will be incorporated into the asn1c command invocation. Specifying a project file in this way is equivalent to using the -proj qualifier described below.

The following table lists all of the command line options and what they are used for. The options are shown in alphabetical order. Note that the Java, C#, Python, and Go options are not shown here. They are shown in their respective documents.