Glossary

Action — an expression element that does something with an entry that reaches it: -print, -ls, -exec, -ok, -delete, -prune. If an expression has no action, find adds -print to the whole of it. Chapters 1, 6, 8.

ARG_MAX — the kernel's cap on the total size of a command's arguments plus its environment; the ceiling xargs exists to work under. Chapter 9.

Basename — the final component of a path: notes.txt in tree/notes.txt. -name tests the basename; -path tests the whole string. Chapter 2.

Broken symlink — a link whose target does not exist. Found by asking for links whose target is a link: -xtype l. Chapter 10.

Depth — distance from the starting point: the start itself is 0, its immediate contents 1. -maxdepth and -mindepth govern the walk by it. Chapter 7.

Entry — anything the walk visits: a file, directory, symlink, device, pipe, or socket. Tests apply to entries of every kind unless -type narrows them. Chapter 1.

Exit code — the number left in $?. find's are 0 (the walk completed, matches or not) and nonzero (something failed). xargs adds 123: a command it ran failed. Chapters 9, 12.

Expression — the tests and actions after the starting points, evaluated left to right, AND binding tighter than -o. Chapters 1, 6.

Glob — the shell's pattern language: * any run of characters, ? exactly one, [...] one of a set. find's -name speaks glob, not regular expression — and the pattern must match the whole name. Chapter 2.

Marker — the reference file in a -newer test: entries are judged against its timestamp. Chapter 4.

mtime — the modification time: when an entry's contents last changed. -mmin tests it in minutes, -mtime in whole days, the fraction discarded. Its siblings are atime (last read) and ctime (last metadata change — not creation). Chapter 4.

NUL — the zero byte, the one character a filename can never contain, and therefore the only separator that cannot lie: -print0 output, read by xargs -0. Chapter 9.

Prune — -prune: when the left side of an expression matches a directory, the walk does not descend into it. Only correct in its -o shape. Chapter 7.

Round up — -size's conversion: a size is reported as the count of whole units it touches, so 1 byte is size 1M and exactly 1 MiB is not +1M. Chapter 3.

Setuid / setgid — the special permission bits (4000 / 2000) that let a program run with its owner's or group's authority; shown as s in a listing, audited with -perm /6000. Chapter 5.

Sparse file — a file whose length is mostly unwritten holes: apparent size large, allocated size (what du reports) small. Chapter 3.

Starting point — a path find is told to walk. It is itself the first entry tested, and it may be a file. Absent, it is .. Chapters 1, 12.

Symlink — an entry that contains a path to another entry. -type l tests the link itself; -xtype tests what it points at. Chapters 2, 10.

Test — an expression element that is true or false of an entry: -name, -type, -size, -mtime, -user, -perm, and their kin. Chapters 1–7.

Walk — find's traversal: each starting point, then its contents, recursively, a directory always before what it holds, in the filesystem's order rather than sorted order. Chapter 1.

World-writable — the o+w permission: anyone may write. Audited with -perm -0002. Chapter 5.