CODEWITHSUNDEEP
bash
Chris
Chris

Reputation: 1697

How to find files containing empty strings

One of our suppliers has a buggy shop floor system (long story short). While they fix whatever is wrong on their end, I need to segregate files they send: they are not empty but have a long empty string. Typically a good file will look like this in vi

    <insert_list><test_event_insert  endTime="2012-09-10T05:28:45" startTime="2012-09-10T05:27:41" operator="8176967"><process_step name="FVT" revision="NO DATA"></process_step><location1 name="CT" type="REGION"><location2 name="ONTREP1" type="TESTER"><location3 name="LineA" type="LINE"></location3></location2></location1><unit ...
"CT~DCA~FVT~8176967~ONTREP1~4~P~1100~DECA1MR0-01~XED1B1033A4675~20120910~052846.XML" [noeol][dos] 3L, 2170C

a bad file will look this:

^@^@^@^@^@^@^@^@^@^@^@^@^@...

"CT~DCA~FVT~8176967~ONTREP1~2~P~1100~DECA1MR0-01~XED1B1045B6072~20120904~043209.XML" [noeol] 1L, 2170C

The caret/at sign combo is VI's interpretation of that string, I guess but it is in fact an empty string. Using -z seems to work on one single file

X=CT~DCA~FVT~8176967~ONTREP1~2~P~1100~DECA1MR0-01~XED1B1045B6072~20120904~043209.XML
if [ ! -z $X ] 
then 
echo "$X empty"
else 
echo "$X not empty"
fi
    CT~DCA~FVT~8176967~ONTREP1~2~P~1100~DECA1MR0-01~XED1B1045B6072~20120904~043209.XML empty

But the same code is telling me that all 900 files on my EMC mass filer are empty. Which is not true.

export OUT=/path/to/device
declare -a myArray
for f in "$OUT"/*ONTREP1*; do myArray+=( "${f#$OUT/}" ); done
for i in "${myArray[@]}"; do  if [ ! -z $i ] ; then echo "$i empty"; else echo "$i not empty"; fi; done

NB: Pattern "ONTREP1" is to narrow down the faulty files to one shop floor computer name.

What am I missing?

Upvotes: 1

Views: 487

Answers (1)

Jens
Jens

Reputation: 72667

You are missing that test -z string tests whether a string is empty (as opposed to test -s file which tests whether a file is empty.) Furthermore the ^@ in vim are an indication of NUL bytes--bytes with the value 0. It looks like these are binary data files or maybe corrupted, but certainly not empty. An empty file in vim displays as all tildes (~) in the leftmost column :-)

Try running the file filename command on the good and bad files; the latter probably says "data" due to the NUL bytes.

Upvotes: 2

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