nm(1p) — Linux manual page


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

PROLOG         top

       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         top

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

SYNOPSIS         top

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

DESCRIPTION         top

       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         top

       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

       -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         top

       The following operand shall be supported:

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

STDIN         top

       See the INPUT FILES section.

INPUT FILES         top

       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.


       The following environment variables shall affect the execution of

       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.

                 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).

                 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.



STDOUT         top

       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

        *  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)

           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,

           "%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         top

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES         top




EXIT STATUS         top

       The following exit values shall be returned:

        0    Successful completion.

       >0    An error occurred.



       The following sections are informative.


       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         top


RATIONALE         top

       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.



SEE ALSO         top

       ar(1p), c99(1p)

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

COPYRIGHT         top

       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)

Pages that refer to this page: c99(1p)strings(1p)