如何从一个.gz 压缩文件获得几行而不解压缩

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最佳答案

zcat(1) can be supplied by either compress(1) or by gzip(1). On your system, it appears to be compress(1) -- it is looking for a file with a .Z extension.

Switch to gzip -cd in place of zcat and your command should work fine:

 gzip -cd CONN.20111109.0057.gz | head

Explanation

   -c --stdout --to-stdout
Write output on standard output; keep original files unchanged.  If there are several input files, the output consists of a sequence of independently compressed members. To obtain better compression, concatenate all input files before compressing
them.


-d --decompress --uncompress
Decompress.

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On some systems (e.g., Mac), you need to use gzcat.

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On a mac you need to use the < with zcat:

zcat < CONN.20111109.0057.gz|head

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If a continuous range of lines needs be, one option might be:

gunzip -c file.gz | sed -n '5,10p;11q' > subFile

where the lines between 5th and 10th lines (both inclusive) of file.gz are extracted into a new subFile. For sed options, refer to the manual.

If every, say, 5th line is required:

gunzip -c file.gz | sed -n '1~5p;6q' > subFile

which extracts the 1st line and jumps over 4 lines and picks the 5th line and so on.

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This awk snippet will let you show not only the first few lines - but a range you can specify. It will also add line numbers which i needed for debugging an error message pointing to a certain line way down in a gzipped file.

gunzip -c file.gz | awk -v from=10 -v to=20 'NR>=from { print NR,$0; if (NR>=to) exit 1}'

Here is the awk snippet used in the one liner above. In awk NR is a built-in variable (Number of records found so far) which usually is equivalent to a line number. the from and to variable are picked up from the command line via the -v options.

NR>=from {
print NR,$0;
if (NR>=to)
exit 1
}

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If you want to use zcat, this will show the first 10 rows

zcat your_filename.gz | head

Let's say you want the 16 first row

zcat your_filename.gz | head -n 16