Cross-platform file compression

zipmerge

zipmerge adds a source archive into a target archive. Use zipmerge carefully, since files in the target will be overwritten by files of the same name in the source. You can reduce the chances of accidental overwriting by using the -i option to verify each overwriting. Similarly, -S will automatically prevent overwriting files with the same size and name on both the source and target. Also avoid using -I to ignore letter case.

Note that zipmerge is not installed automatically. When archives merge, both the original files remain, and the only indication of the merge is that the target file is larger.

zipnote

zipnote is used to read and edit comments in archives. To read an archive's comment, pipe it to standard output with:

zipnote FILE-NAME.zip > FILE-NAME.tmp

Open FILE-NAME.tmp to read and edit. Then add the updated comment with:

zipnote -w FILE-NAME.zip < FILE-NAME.tmp

zipnote is particularly useful for changing file names in an archive that start with @home in the comment. However, remember to keep the original extensions.

zipsplit

zipsplit divides existing archives into smaller ones, creating an index file to help reassemble them (Figure 6). You might want to divide an archive for two reasons: To reduce any loss of data due to corruption and to store the files across multiple volumes. The default file size is 36KB, but it can be edited using the -n option, although the maximum size is 2GB. If you do edit the file size, then you should probably add -t to do a dry run and see how many files you will create. Use zipmerge to reassemble the original archive. As an alternative, you can use the --split-size option.

Figure 6: zipsplit divides an archive into smaller ones.

The output will consist of eight character files, each ending in a number. The first seven characters will be the first seven letters of the original file name.

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