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### 2.2 Environment Variables

You can change the behaviour of `ld` with the environment variables `GNUTARGET`, `LDEMULATION` and `COLLECT_NO_DEMANGLE`.

`GNUTARGET` determines the input-file object format if you don't use ‘`-b`’ (or its synonym ‘`--format`’). Its value should be one of the BFD names for an input format (see BFD). If there is no `GNUTARGET` in the environment, `ld` uses the natural format of the target. If `GNUTARGET` is set to `default` then BFD attempts to discover the input format by examining binary input files; this method often succeeds, but there are potential ambiguities, since there is no method of ensuring that the magic number used to specify object-file formats is unique. However, the configuration procedure for BFD on each system places the conventional format for that system first in the search-list, so ambiguities are resolved in favor of convention.

`LDEMULATION` determines the default emulation if you don't use the ‘`-m`’ option. The emulation can affect various aspects of linker behaviour, particularly the default linker script. You can list the available emulations with the ‘`--verbose`’ or ‘`-V`’ options. If the ‘`-m`’ option is not used, and the `LDEMULATION` environment variable is not defined, the default emulation depends upon how the linker was configured.

Normally, the linker will default to demangling symbols. However, if `COLLECT_NO_DEMANGLE` is set in the environment, then it will default to not demangling symbols. This environment variable is used in a similar fashion by the `gcc` linker wrapper program. The default may be overridden by the ‘`--demangle`’ and ‘`--no-demangle`’ options.