12-18-2016
Let me applaud you to your efforts to circumnavigate the problems you encountered and to your (can I say: ) endurance in finding a solution on your own, as opposed to coming back whining immediately. Other members could certainly take a leaf out of your book!
Trying to answer some of your questions:
- I'd be surprised if extra lines were added if the loop starts with i=1, at least it didn't when I tested it. And, why should it?
- /var/ in awk is a regex constant, so it would try to match the sequence of chars'v', 'a', and 'r'. Your last approach is the right one to match variables.
- awk works on pattern {action} pairs. action is executed if pattern is TRUE. So, F is equivalent to F != 0 as awk treats 0 as FALSE and anything else as TRUE.
- shell scripts are interpreted line by line, even in a loop, and files for e.g. output are opened and closed for every redirection encountered (e.g. echo or printf command). awk reads a script, compiles, and executes it. Files are kept open unless explicitly closed. This will make up for the main execution time difference. Although you are not using external commands (which would consume resources for a process creation for each and make it even slower), some of your statements could be improved.
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fwtmp(1M) fwtmp(1M)
NAME
fwtmp, wtmpfix - manipulate connect accounting records
SYNOPSIS
[files]
DESCRIPTION
fwtmp
reads from the standard input and writes to the standard output, converting binary records of the type found in to formatted ASCII records.
The ASCII version is useful to enable editing, via ed(1), bad records or for general purpose maintenance of the file.
The argument is used to denote that input is in ASCII form, and output is to be written in binary form. The arguments and are independent,
respectively specifying ASCII input and binary output. Therefor, is an ASCII to ASCII copy and is a binary to binary copy. should be used
for reading If is not used, structure is read.
wtmpfix
examines the standard input or named files in format, corrects the time/date stamps to make the entries consistent, and writes to the stan-
dard output. A can be used in place of files to indicate the standard input. If time/date corrections are not performed, will fault when
it encounters certain date-change records.
Each time the date is set, a pair of date change records is written to The first record is the old date denoted by the string old time
placed in the line field and the flag placed in the type field of the structure. The second record specifies the new date, and is denoted
by the string placed in the line field and the flag placed in the type field. uses these records to synchronize all time stamps in the
file. nullifies date change records when writing to the standard output by setting the time field of the structure in the old date change
record equal to the time field in the new date change record. This prevents and from factoring in a date change record pair more than
once.
In addition to correcting time/date stamps, wtmpfix checks the validity of the name field to ensure that it consists solely of alphanumeric
characters or spaces. If it encounters a name that is considered invalid, it changes the login name to and writes a diagnostic to the
standard error. This minimizes the risk that will fail when processing connect accounting records.
DIAGNOSTICS
wtmpfix generates the following diagnostics messages:
WARNINGS
generates no errors, even on garbage input.
FILES
SEE ALSO
ed(1), acct(1M), acctcms(1M), acctcom(1M), acctcon(1M), acctmerg(1M), acctprc(1M), acctsh(1M), runacct(1M), acct(2), acct(4), utmp(4),
wtmps(4).
STANDARDS CONFORMANCE
fwtmp(1M)