nm [-APv][-efox][ -g| -u][-t format] file...
This utility shall be provided on systems that support both the User Portability Utilities option and the Software Development Utilities option. On other systems it is optional. Certain options are only available on XSI-conformant systems.
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.
The nm utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
The following options shall be supported:
The following operand shall be supported:
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:
Determine the locale for character collation information for the symbol-name and symbol-value collation sequences.
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 alphabetically by symbol name:
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>
"%s: ", <file>
"%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:
"%s:\n", <file>
"%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.
The standard error shall be used only for diagnostic messages.
The following exit values shall be returned:
Default.
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.
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 spaces between the fields, which may be any number of <blank>s 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.