nm

NM(1P)                      POSIX Programmer's Manual                     NM(1P)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the corresponding
       Linux manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.

NAME
       nm — write the name list of an object file (DEVELOPMENT)

SYNOPSIS
       nm [-APv] [-g|-u] [-t format] file...
       nm [-APv] [-efox] [-g|-u] [-t format] file...

DESCRIPTION
       The nm utility shall display symbolic information appearing in the object
       file, executable file, or object-file library named by file.  If no
       symbolic information is available for a valid input file, the nm utility
       shall report that fact, but not consider it an error condition.

       The default base used when numeric values are written is unspecified.  On
       XSI-conformant systems, it shall be decimal if the -P option is not
       specified.

OPTIONS
       The nm utility shall conform to the Base Definitions volume of
       POSIX.1‐2017, Section 12.2, Utility Syntax Guidelines.

       The following options shall be supported:

       -A        Write the full pathname or library name of an object on each
                 line.

       -e        Write only external (global) and static symbol information.

       -f        Produce full output. Write redundant symbols (.text, .data, and
                 .bss), normally suppressed.

       -g        Write only external (global) symbol information.

       -o        Write numeric values in octal (equivalent to -t o).

       -P        Write information in a portable output format, as specified in
                 the STDOUT section.

       -t format Write each numeric value in the specified format. The format
                 shall be dependent on the single character used as the format
                 option-argument:

                 d     decimal (default if -P is not specified).

                 o     octal.

                 x     hexadecimal (default if -P is specified).

       -u        Write only undefined symbols.

       -v        Sort output by value instead of by symbol name.

       -x        Write numeric values in hexadecimal (equivalent to -t x).

OPERANDS
       The following operand shall be supported:

       file      A pathname of an object file, executable file, or object-file
                 library.

STDIN
       See the INPUT FILES section.

INPUT FILES
       The input file shall be an object file, an object-file library whose
       format is the same as those produced by the ar utility for link editing,
       or an executable file. The nm utility may accept additional
       implementation-defined object library formats for the input file.

ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of nm:

       LANG      Provide a default value for the internationalization variables
                 that are unset or null. (See the Base Definitions volume of
                 POSIX.1‐2017, Section 8.2, Internationalization Variables for
                 the precedence of internationalization variables used to
                 determine the values of locale categories.)

       LC_ALL    If set to a non-empty string value, override the values of all
                 the other internationalization variables.

       LC_COLLATE
                 Determine the locale for character collation information for
                 the symbol-name and symbol-value collation sequences.

       LC_CTYPE  Determine the locale for the interpretation of sequences of
                 bytes of text data as characters (for example, single-byte as
                 opposed to multi-byte characters in arguments).

       LC_MESSAGES
                 Determine the locale that should be used to affect the format
                 and contents of diagnostic messages written to standard error.

       NLSPATH   Determine the location of message catalogs for the processing
                 of LC_MESSAGES.

ASYNCHRONOUS EVENTS
       Default.

STDOUT
       If symbolic information is present in the input files, then for each file
       or for each member of an archive, the nm utility shall write the
       following information to standard output. By default, the format is
       unspecified, but the output shall be sorted by symbol name according to
       the collation sequence in the current locale.

        *  Library or object name, if -A is specified

        *  Symbol name

        *  Symbol type, which shall either be one of the following single
           characters or an implementation-defined type represented by a single
           character:

           A     Global absolute symbol.

           a     Local absolute symbol.

           B     Global ``bss'' (that is, uninitialized data space) symbol.

           b     Local bss symbol.

           D     Global data symbol.

           d     Local data symbol.

           T     Global text symbol.

           t     Local text symbol.

           U     Undefined symbol.

        *  Value of the symbol

        *  The size associated with the symbol, if applicable

       This information may be supplemented by additional information specific
       to the implementation.

       If the -P option is specified, the previous information shall be
       displayed using the following portable format. The three versions differ
       depending on whether -t d, -t o, or -t x was specified, respectively:


           "%s%s %s %d %d\n", <library/object name>, <name>, <type>,
               <value>, <size>

           "%s%s %s %o %o\n", <library/object name>, <name>, <type>,
               <value>, <size>

           "%s%s %s %x %x\n", <library/object name>, <name>, <type>,
               <value>, <size>

       where <library/object name> shall be formatted as follows:

        *  If -A is not specified, <library/object name> shall be an empty
           string.

        *  If -A is specified and the corresponding file operand does not name a
           library:


               "%s: ", <file>

        *  If -A is specified and the corresponding file operand names a
           library. In this case, <object file> shall name the object file in
           the library containing the symbol being described:


               "%s[%s]: ", <file>, <object file>

       If -A is not specified, then if more than one file operand is specified
       or if only one file operand is specified and it names a library, nm shall
       write a line identifying the object containing the following symbols
       before the lines containing those symbols, in the form:

        *  If the corresponding file operand does not name a library:


               "%s:\n", <file>

        *  If the corresponding file operand names a library; in this case,
           <object file> shall be the name of the file in the library containing
           the following symbols:


               "%s[%s]:\n", <file>, <object file>

       If -P is specified, but -t is not, the format shall be as if -t x had
       been specified.

STDERR
       The standard error shall be used only for diagnostic messages.

OUTPUT FILES
       None.

EXTENDED DESCRIPTION
       None.

EXIT STATUS
       The following exit values shall be returned:

        0    Successful completion.

       >0    An error occurred.

CONSEQUENCES OF ERRORS
       Default.

       The following sections are informative.

APPLICATION USAGE
       Mechanisms for dynamic linking make this utility less meaningful when
       applied to an executable file because a dynamically linked executable may
       omit numerous library routines that would be found in a statically linked
       executable.

EXAMPLES
       None.

RATIONALE
       Historical implementations of nm have used different bases for numeric
       output and supplied different default types of symbols that were
       reported. The -t format option, similar to that used in od and strings,
       can be used to specify the numeric base; -g and -u can be used to
       restrict the amount of output or the types of symbols included in the
       output.

       The compromise of using -t format versus using -d, -o, and other similar
       options was necessary because of differences in the meaning of -o between
       implementations. The -o option from BSD has been provided here as -A to
       avoid confusion with the -o from System V (which has been provided here
       as -t and as -o on XSI-conformant systems).

       The option list was significantly reduced from that provided by
       historical implementations.

       The nm description is a subset of both the System V and BSD nm utilities
       with no specified default output.

       It was recognized that mechanisms for dynamic linking make this utility
       less meaningful when applied to an executable file (because a dynamically
       linked executable file may omit numerous library routines that would be
       found in a statically linked executable file), but the value of nm during
       software development was judged to outweigh other limitations.

       The default output format of nm is not specified because of differences
       in historical implementations.  The -P option was added to allow some
       type of portable output format. After a comparison of the different
       formats used in SunOS, BSD, SVR3, and SVR4, it was decided to create one
       that did not match the current format of any of these four systems. The
       format devised is easy to parse by humans, easy to parse in shell
       scripts, and does not need to vary depending on locale (because no
       English descriptions are included).  All of the systems currently have
       the information available to use this format.

       The format given in nm STDOUT uses <space> characters between the fields,
       which may be any number of <blank> characters required to align the
       columns. The single-character types were selected to match historical
       practice, and the requirement that implementation additions also be
       single characters made parsing the information easier for shell scripts.

FUTURE DIRECTIONS
       None.

SEE ALSO
       ar, c99

       The Base Definitions volume of POSIX.1‐2017, Chapter 8, Environment
       Variables, Section 12.2, Utility Syntax Guidelines

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute
       of Electrical and Electronics Engineers, Inc and The Open Group.  In the
       event of any discrepancy between this version and the original IEEE and
       The Open Group Standard, the original IEEE and The Open Group Standard is
       the referee document. The original Standard can be obtained online at
       http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are most
       likely to have been introduced during the conversion of the source files
       to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                   2017                                NM(1P)