How to get few lines from a .gz compressed file without uncompressing

Solution 1:

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.

Solution 2:

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

Solution 3:

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

zcat < CONN.20111109.0057.gz|head

Solution 4:

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.