03-01-2019
Shell evaluation is done automatically, by the shell, before a command is run. None of these except eval do shell evaluation; eval can do so because it's actually part of the shell!
By the same ticket, ls abc* is not a feature of ls. abc* gets evaluated by the shell before ls is executed.
I'm not sure what your >stdin stdin> are about. eval does not use stdin or stdout especially, unless the command it's evaluating does. It has no limits at all. That's what makes it dangerous.
One unique feature of xargs is that it parses single and double quotes. Usually this is considered an annoyance and worked around, but this can be used to your advantage, i.e. to split strings containing quotes without resorting to eval.
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LEARN ABOUT OPENSOLARIS
eval
eval(1T) Tcl Built-In Commands eval(1T)
__________________________________________________________________________________________________________________________________________________
NAME
eval - Evaluate a Tcl script
SYNOPSIS
eval arg ?arg ...?
_________________________________________________________________
DESCRIPTION
Eval takes one or more arguments, which together comprise a Tcl script containing one or more commands. Eval concatenates all its argu-
ments in the same fashion as the concat command, passes the concatenated string to the Tcl interpreter recursively, and returns the result
of that evaluation (or any error generated by it). Note that the list command quotes sequences of words in such a way that they are not
further expanded by the eval command.
EXAMPLE
This procedure acts in a way that is analogous to the lappend command, except it inserts the argument values at the start of the list in
the variable:
proc lprepend {varName args} {
upvar 1 $varName var
# Ensure that the variable exists and contains a list
lappend var
# Now we insert all the arguments in one go
set var [eval [list linsert $var 0] $args]
}
KEYWORDS
concatenate, evaluate, script
SEE ALSO
catch(1T), concat(1T), error(1T), list(1T), subst(1T), tclvars(1T)
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Availability | SUNWTcl |
+--------------------+-----------------+
|Interface Stability | Uncommitted |
+--------------------+-----------------+
NOTES
Source for Tcl is available on http://opensolaris.org.
Tcl eval(1T)