Touch (command)

Article summary

touch is a shell command that sets the modification timestamp of an existing file to be current which on a Unix-based file system includes special files such as directories. If the input path does not specify an existing file, then it creates a new, regular file at the path. The Single UNIX Specification (SUS) specifies that touch changes the access or modification timestamps, or both. The file is identified by file system path supplied as the sole argument. If the path does not specify a file, the command creates a file with access and modification timestamps as specified or by default to the current time. By default (no options specified), touching a file is equivalent to creating it with no content or if it exists, opening and saving it without any content changes to update the modification timestamp to be current. This convenience functionality is useful for a variety of scenarios including build and backup. The tools used in such scenarios typically ignore files that are older than a certain point of time. For example, make ignores a source code file that is older than the object file it is used to create. The command is often used to create a new file, so that can subsequently open it in an editor or to create a file required by an operation that does not require specific content. A touch command first appeared in Version 7 AT&T UNIX.…

Key claims

No claims recorded.

Discussion questions

1. Summarise the article in your own words. Which single claim would you verify first, and why?
2. Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
3. If two sources disagreed about one of these facts, what would you need in order to trust one over the other?

Bibliography

No sources recorded.