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v2.05b - Bot T19 CW#25 - Fix errors for CW project (Heading hierarchy)

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{{Short description|Unix command}}
{{lowercase}}
The '''script''' command is a [[Unix utility]] that records a [[computer terminal|terminal]] session. It dates back to the 1979 3.0 [[Berkeley Software Distribution]] (BSD).<ref name="man">{{man|1|script|FreeBSD}}</ref>

== Usage ==
A script session is captured in file name {{code|typescript}} by default; to specify a different filename follow the {{code|script}} command with a space and the filename as such: {{code|script recorded_session}}.

The recorded format of {{code|script}} consists of plain-text timing information (for the whole session) and verbatim command output, including whatever [[ANSI escape code]] the program has printed for formatting. It uses a [[pseudoterminal]] for this purpose, so programs act exactly as if they were on a terminal.<ref name="man" /> The [[util-linux]] {{code|scriptreplay}} command offers a replay function to its script, which supports using an extra timing file for character-level information.<ref>{{man|1|scriptreplay|Linux}}</ref><ref>[http://www.linuxinsight.com/replaying-terminal-sessions-with-scriptreplay.html LinuxInsight - Replaying terminal sessions with scriptreplay]</ref> Some online services, such as the now-defunct shelr.tv, can also show the format as a low-bandwidth alternative to video screencasts.<ref>[http://www.omgubuntu.co.uk/2012/04/how-to-record-and-share-terminal-screencasts-quickly/ OMG! Ubuntu! - How To Record And Share Terminal Screencasts Quickly]</ref>

== Problems with script command ==
One of the problems with the script command is that it only allows logging of a child process; and often there is a need to log the command in the current process without spawning a new process, such as when automation of a script is needed that can log its own output. The [[Unix]] operating systems make this possible by use of [[Pipe (Unix)|pipe]]s and redirects. Consider the following model examples:

=== Bourne shell ===

All [[Unix shell|shells]] related to [[Bourne shell]] (<code>sh</code>), for example [[Thompson shell]] (<code>sh</code>), [[Bash (Unix shell)|Bash]] (<code>bash</code>), [[KornShell]] (<code>ksh</code>), and [[Z shell]] (<code>zsh</code>), allow the [[stdout]] and [[stderr]] to be attached to a [[named pipe]] and redirected to the [[tee (command)|tee command]], for example:

<syntaxhighlight lang="bash">
LOGNAME="script"
rm -f $LOGNAME.p $LOGNAME.log
mknod $LOGNAME.p p
tee <$LOGNAME.p $LOGNAME.log &
exec >$LOGNAME.p 2>&1
</syntaxhighlight>

The above script records to {{code|script.log}} all output of the {{code|exec}} command. However, some interactive programs (such as [[Python (programming language)|Python]]) do not echo their standard input when run under the resulting shell, although they do when run under the script command, again due to the detection of a terminal.

== Alternatives to script command==
The [[ttyrec]] program from 2000 provides the same kind of functionality and offers several bindings. The timing is similar to util-linux. A more modern take on the concept is "asciicast" [[JSON]], used by asciinema.<ref>{{Cite web|url=https://asciinema.org/about|title=About - asciinema}}</ref>

== See also ==
* [[Command line interpreter]]
* [[Shebang (Unix)]]
* [[C shell]]
* [[Filename extension]]
* [[Perl]]
* [[Scripting language]]

== References ==
{{Reflist}}

[[Category:Unix software]]

Script (Unix) - Revision history

imported>WikiCleanerBot: v2.05b - Bot T19 CW#25 - Fix errors for CW project (Heading hierarchy)