Please find my OS details:
$ uname -a
AIX xxyy 1 6 000145364C00I've tried the following command to get size of a file in gzip archive:
$ gzip -l mycontent.DAT.Gz
compressed uncompr. ratio uncompressed_name
-1223644243 1751372002 -75.3% mycontent.DAT.GzNot sure how to interpret the unzipped size from this. Compressed file size close to 4 GB.
So, I tried this option in order to capture correct data:
$ zcat mycontent.DAT.Gz | wc -cIt gives me this error:
mycontent.DAT.Gz.Z:A file or directory in the path name does not exist.
0Can you please tell me how to capture this value from shell script without decompressing the source file?
16 Answers
To answer the question title:
How can I get the uncompressed size of gzip file without actually decompressing it?
As you obviously know, the option -l (--list) is usually showing the uncompressed size.
What it shows is not calculated from the data, but was stored in the header as part of the compressed file.
In your case, the -l option does not work for some reason.
But it's not possible to 'measure' the uncompressed size from the raw compressed data - there is just no information about anything else in the compressed data - which is not surprising, as the point of compression is to leave out anything not needed.
You do not need to store the uncompressed data on the disk: zcat file.gz | wc -c is the right approach - but as @OleTange answered, your zcat seems to be not the one from gzip.
The alternative is using the gzip options -d (--decompress) and -c (--to-stdout), combined with wc option -c (--bytes):
gzip -dc file.gz | wc -cYour zcat is not GNU zcat but from compress. Try:
gzcat mycontent.DAT.Gz | LC_ALL=C wc -c
gzip -dc mycontent.DAT.Gz | LC_ALL=C wc -cI like using pv as it shows a more human readable information and progress:
zcat file.gz | pv > /dev/nullOutputs:
7,65GiB 0:00:44 [ 174MiB/s] [Unfortunately, the only way to know is to extract it and count the bytes. gzip files do not properly report uncompressed data >4GB in size. See RFC1952, which defines the gzip file format:
ISIZE (Input SIZE) This contains the size of the original (uncompressed) input data modulo 2^32.This discrepancy might be a little more obvious if whatever version of gzip you are using didn't have a bug: it is treating the ISIZE value as a signed 32-bit integer (resulting in -1223644243), rather than an unsigned 32-bit integer (which would result in 3071323053).
The most you can determine based on the header alone is that the real size of the uncompressed data is
(n * 4,294,967,296) + 3,071,323,053where n is some whole number.
I'm finding everything sites in the web, and don't resolve this problem the get size when file size is bigger of 4GB.
my solution is this:
[oracle@base tmp]$ timeout --signal=SIGINT 1s tar -tvf oracle.20180303.030001.dmp.tar.gz -rw-r--r-- oracle/oinstall 111828 2018-03-03 03:05 oracle.20180303.030001.log -rw-r----- oracle/oinstall 6666911744 2018-03-03 03:05 oracle.20180303.030001.dmp
for get total size from gz file:
[oracle@base tmp]$ echo $(timeout --signal=SIGINT 1s tar -tvf oracle.20180303.030001.dmp.tar.gz | awk '{print $3}') | grep -o '[[:digit:]]*' | awk '{ sum += $1 } END { print sum }' 6667023572 1 gzip -l did not work for me, just git -1 ... but this did:
unzip -l file.zip
