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Top Forums Shell Programming and Scripting Difference between "Command substitution" and "Process substitution" Post 302268287 by Christoph Spohr on Monday 15th of December 2008 10:20:15 AM
Old 12-15-2008
Hi,

$(...) means execute the command ... and print the output
to the command line.
<(...) and =(...) create a temporary file of the output and
redirect the output of this to the command line.

To understand the difference try:

Code:
diff $(ls) $(ls)

and

Code:
diff <(ls) <(ls)

The first will fail as diff expects input from a file.

HTH Chris
 

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Tcl_RecordAndEvalObj(3) 				      Tcl Library Procedures					   Tcl_RecordAndEvalObj(3)

__________________________________________________________________________________________________________________________________________________

NAME
Tcl_RecordAndEvalObj - save command on history list before evaluating SYNOPSIS
#include <tcl.h> int Tcl_RecordAndEvalObj(interp, cmdPtr, flags) ARGUMENTS
Tcl_Interp *interp (in) Tcl interpreter in which to evaluate command. Tcl_Obj *cmdPtr (in) Points to a Tcl object containing a command (or sequence of commands) to execute. int flags (in) An OR'ed combination of flag bits. TCL_NO_EVAL means record the command but don't evaluate it. TCL_EVAL_GLOBAL means evaluate the command at global level instead of the current stack level. _________________________________________________________________ DESCRIPTION
Tcl_RecordAndEvalObj is invoked to record a command as an event on the history list and then execute it using Tcl_EvalObjEx (or Tcl_Global- EvalObj if the TCL_EVAL_GLOBAL bit is set in flags). It returns a completion code such as TCL_OK just like Tcl_EvalObjEx, as well as a result object containing additional information (a result value or error message) that can be retrieved using Tcl_GetObjResult. If you don't want the command recorded on the history list then you should invoke Tcl_EvalObjEx instead of Tcl_RecordAndEvalObj. Normally Tcl_RecordAndEvalObj is only called with top-level commands typed by the user, since the purpose of history is to allow the user to re- issue recently-invoked commands. If the flags argument contains the TCL_NO_EVAL bit then the command is recorded without being evaluated. SEE ALSO
Tcl_EvalObjEx, Tcl_GetObjResult KEYWORDS
command, event, execute, history, interpreter, object, record Tcl 8.0 Tcl_RecordAndEvalObj(3)
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