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Comment by vorador | Hacker News Reader

Does someone know what's this use of grep as cat he alludes at ?

You can use

  grep '.*' > /etc/password

instead of

  cat > /etc/password

since echo still worked, why would you need grep for that one?

Because it does something entirely different. "echo " is the same as "ls", while "grep '.'" is the same as "cat".

echo, as he says, was built into the korn shell, whereas grep was a binary he deleted from the filesystem.

Perhaps using grep to match anything and thus output the whole file?

    grep '.*' file

Match any non-empty line.

   /usr/bin/grep ".*" /path/of/file

Sod any 'non-empty line'

  /usr/bin/grep '^' > output

Or even better, grep can be an editor with line filtering - if you make an mistake, have it throw away the line:

  /usr/bin/grep -v '%' > output

(Any line with a %, throw away, keep the rest - good for multi-line files)

That command actually matches any line. You seem to have confused it with egrep ".+".