- published: 02 May 2016
- views: 26883
In Unix-like and some other operating systems, find
is a command-line utility that searches through one or more directory trees of a file system, locates files based on some user-specified criteria and applies a user-specified action on each matched file. The possible search criteria include a pattern to match against the file name or a time range to match against the modification time or access time of the file. By default, find
returns a list of all files below the current working directory.
The related locate
programs use a database of indexed files obtained through find
(updated at regular intervals, typically by cron
job) to provide a faster method of searching the entire filesystem for files by name. This sacrifices overall efficiency (because filesystems are regularly interrogated even when no user needs information) and absolute accuracy (since the database is not updated in real time) for significant speed improvements (particularly on very large filesystems). On fast systems with small drives, locate
is neither necessary nor desirable.
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation. Adaptations contribute to the fitness and survival of individuals. Organisms face a succession of environmental challenges as they grow and develop and are equipped with an adaptive plasticity as the phenotype of traits develop in response to the imposed conditions. The developmental norm of reaction for any given trait is essential to the correction of adaptation as it affords a kind of biological insurance or resilience to varying environments.
The significance of an adaptation can only be understood in relation to the total biology of the species.
Adaptation is, first of all, a process, rather than a physical part of a body. An internal parasite (such as a fluke) can illustrate the distinction: such a parasite may have a very simple bodily structure, but nevertheless the organism is highly adapted to its specific environment. From this we see that adaptation is not just a matter of visible traits: in such parasites critical adaptations take place in the life-cycle, which is often quite complex. However, as a practical term, adaptation is often used for the product: those features of a species which result from the process. Many aspects of an animal or plant can be correctly called adaptations, though there are always some features whose function is in doubt. By using the term adaptation for the evolutionary process, and adaptive trait for the bodily part or function (the product), the two senses of the word may be distinguished.