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Full Discussion: awk last n lines of file
Top Forums Shell Programming and Scripting awk last n lines of file Post 302905879 by 1in10 on Sunday 15th of June 2014 06:58:37 PM
Old 06-15-2014
@Don Cragun
Much ambition means many errors, no errors means no trouble at all, I agree that this is a task for me.
From the very outset I want to set this file to just 200 entries, nothing more. And catch the last seven and in a furhter step the last thirty lines of the fifth field for a calculation. The text-string " swap " could be any other. BTW I am not a pro so: I do not know anything about circular buffers, excuse me.
My OS here is debian wheezy 7.5, no server.
So I cut out the first statement do direct it after the awk-statement to the stdout. As you may see, this could be a beginner, but I assure you I am right in the middle, because this is my third week around with awk.
 

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catch(n)						       Tcl Built-In Commands							  catch(n)

__________________________________________________________________________________________________________________________________________________

NAME
catch - Evaluate script and trap exceptional returns SYNOPSIS
catch script ?varName? _________________________________________________________________ DESCRIPTION
The catch command may be used to prevent errors from aborting command interpretation. Catch calls the Tcl interpreter recursively to exe- cute script, and always returns without raising an error, regardless of any errors that might occur while executing script. If script raises an error, catch will return a non-zero integer value corresponding to one of the exceptional return codes (see tcl.h for the definitions of code values). If the varName argument is given, then the variable it names is set to the error message from interpret- ing script. If script does not raise an error, catch will return 0 (TCL_OK) and set the variable to the value returned from script. Note that catch catches all exceptions, including those generated by break and continue as well as errors. The only errors that are not caught are syntax errors found when the script is compiled. This is because the catch command only catches errors during runtime. When the catch statement is compiled, the script is compiled as well and any syntax errors will generate a Tcl error. EXAMPLES
The catch command may be used in an if to branch based on the success of a script. if { [catch {open $someFile w} fid] } { puts stderr "Could not open $someFile for writing $fid" exit 1 } The catch command will not catch compiled syntax errors. The first time proc foo is called, the body will be compiled and a Tcl error will be generated. proc foo {} { catch {expr {1 +- }} } KEYWORDS
catch, error Tcl 8.0 catch(n)
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