man -k : nothing appropriate.

➜  workplace man -k zip
zip: nothing appropriate.

出现这种情况，是索引库没有建立。

man 和 whatis 共用一个索引库的。

我们使用  man whatis 进行查看：

       index databases are used during the search, and are updated by  the  mandb  pro‐
       gram.   Depending  on your installation, this may be run by a periodic cron job,
       or may need to be run manually after new manual pages have been  installed.   To
       produce  an  old  style  text  whatis database from the relative index database,
       issue the command:

所以进行执行 mandb 就行了。 老版本的 linux 需要执行： /usr/sbin/makewhatis

这些命令都是在 root 模式下执行。执行后我们重新查看：

➜  ~ man -k zip
bunzip2 (1)          - a block-sorting file compressor, v1.0.6
bzcmp (1)            - compare bzip2 compressed files
bzdiff (1)           - compare bzip2 compressed files
bzegrep (1)          - search possibly bzip2 compressed files for a regular expression
bzfgrep (1)          - search possibly bzip2 compressed files for a regular expression
bzgrep (1)           - search possibly bzip2 compressed files for a regular expression
bzip2 (1)            - a block-sorting file compressor, v1.0.6
bzip2recover (1)     - recovers data from damaged bzip2 files
bzless (1)           - file perusal filter for crt viewing of bzip2 compressed text
bzmore (1)           - file perusal filter for crt viewing of bzip2 compressed text
funzip (1)           - filter for extracting from a ZIP archive in a pipe
gpg-zip (1)          - Encrypt or sign files into an archive
grubby (8)           - command line tool for configuring grub, lilo, elilo, yaboot and ...
gunzip (1)           - compress or expand files
gzip (1)             - compress or expand files
mzip (1)             - change protection mode and eject disk on Zip/Jaz drive
prezip-bin (1)       - prefix zip delta word list compressor/decompressor
unzip (1)            - list, test and extract compressed files in a ZIP archive
unzipsfx (1)         - self-extracting stub for prepending to ZIP archives
zforce (1)           - force a '.gz' extension on all gzip files
zip (1)              - package and compress (archive) files
zipcloak (1)         - encrypt entries in a zipfile
zipgrep (1)          - search files in a ZIP archive for lines matching a pattern
zipinfo (1)          - list detailed information about a ZIP archive
zipnote (1)          - write the comments in zipfile to stdout, edit comments and renam...
zipsplit (1)         - split a zipfile into smaller zipfiles
➜  ~

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