HP-UX Reference (11i v2 04/09) - 1 User Commands N-Z (vol 2)

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sh-posix(1) sh-posix(1)
time pipeline
Execute the pipeline and print the elapsed time, the user time, and the system time on standard
error. Note that the
time keyword can appear anywhere in the pipeline to time the entire pipe-
line. To time a particular command in a pipeline , see time(1).
until list ;dolist ; done
Execute the until list. If the exit status of the last command in the list is nonzero, execute the
do
list and execute the until list again. When the exit status of the last command in the
until list
is zero, terminate the loop. If no commands in the
do list are executed, until returns a zero exit
status.
while list ;dolist ; done
Execute the while list. If the exit status of the last command in the list is zero, execute the
do list
and execute the
while list again. When the exit status of the last command in the
while list is
nonzero, terminate the loop. If no commands in the
do list are executed, while returns a nonzero
exit status.
( list )
Execute list in a separate environment. If two adjacent open parentheses are needed for nesting, a
space must be inserted between them to avoid arithmetic evaluation.
{ list ;}
Execute list, but not in a separate environment. Note that { is a keyword and requires a trailing
blank to be recognized.
[[ expression ]]
Evaluate expression and return a zero exit status when expression is true. See the Conditional
Expressions subsection for a description of expression . Note that [[ and ]] are keywords and
require blanks between them and expression .
Special Commands
Special commands are simple commands that are executed in the shell process. They permit input/output
redirection. Unless otherwise indicated, file descriptor 1 (standard output) is the default output location
and the exit status, when there are no syntax errors, is zero.
Commands that are marked with "%" are treated specially in the following ways:
1. Variable assignment lists preceding the command remain in effect when the command completes.
2. I/O redirections are processed after variable assignments.
3. Certain errors cause a script that contains them to abort.
Words following commands marked with "&" that are in the format of a variable assignment are
expanded with the same rules as a variable assignment. This means that tilde substitution is performed
after the
= sign and word-splitting and file-name generation are not performed.
%
: [arg]...
(colon) Only expand parameters. A zero exit status is returned.
%
. file [arg]...
(period) Read and execute commands from file and return. The commands are executed in the
current shell environment. The search path specified by PATH is used to find the directory contain-
ing file. If any arguments arg are given, they become the positional parameters. Otherwise, the
positional parameters are unchanged. The exit status is the exit status of the last command exe-
cuted.
&
alias [-tx][name[=value] ]...
With name
=value specified, define name as an alias and assign it the value value . A trailing space
in value causes the next word to be checked for alias substitution.
With name
=value omitted, print the list of aliases in the form name=value on standard output.
With name specified without
=value, print the specified alias.
With
-t, set tracked aliases. The value of a tracked alias is the full path name corresponding to the
given name. The value of a tracked alias becomes undefined when the value of PATH is reset, but
Section 1−−848 Hewlett-Packard Company − 4 − HP-UX 11i Version 2: September 2004