PATH

Used by execvp, execlp, and posix_spawnp as specified in POSIX.

TZ

Specifies the local timezone to be used for functions which deal with local time. The value of TZ can be either a POSIX timezone specification in the form stdoffset[dst[offset][,start[/time],end[/time]] or the name of a zoneinfo-binary-format timezone file (the form used by glibc and almost all other systems). The zoneinfo file is interpreted as an absolute pathname if it begins with a slash, a relative pathname if it begins with a dot, and otherwise is searched in /usr/share/zoneinfo, /share/zoneinfo, and /etc/zoneinfo. When searching these paths, strings including any dots are rejected.

DATEMSK

Used by the getdate function as a pathname for the file containing date formats to scan, per POSIX.

PWD

Used by the nonstandard get_current_dir_name function; if it matches the actual current directory, it is returned instead of using getcwd to obtain the canonical pathname.

LOGNAME

The getlogin function simply returns the value of the LOGNAME variable.

LD_PRELOAD

Colon-separated list of shared libraries that will be preloaded by the dynamic linker before processing the application’s dependency list. Components can be absolute or relative pathnames or filenames in the default library search path.

This variable is completely ignored in programs invoked setuid, setgid, or with other elevated capabilities.

LD_LIBRARY_PATH

Colon-separated list of pathnames that will be searched for shared libraries requested without an explicit pathname. This path is searched prior to the default path (which is specified in $(syslibdir)/../etc/ld-musl-$(ARCH).path with built-in default fallback if this file is missing).

This variable is completely ignored in programs invoked setuid, setgid, or with other elevated capabilities.