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

       The default base used when numeric values are written is unspecified.
       On XSI-conformant systems, it shall be decimal.

OPTIONS         top

       The nm utility shall conform to the Base Definitions volume of
       POSIX.1‐2008, 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     The offset is written in decimal (default).

                 o     The offset is written in octal.

                 x     The offset is written in hexadecimal.

       −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 nm:

       LANG      Provide a default value for the internationalization
                 variables that are unset or null. (See the Base Definitions
                 volume of POSIX.1‐2008, Section 8.2, Internationalization
                 Variables for the precedence of internationalization
                 variables used to determine the values of locale

       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 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,

           "%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

        *  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

        *  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

       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

       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.1‐2008, 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, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) 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.unix.org/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                 2013                              NM(1P)

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