xzgrep invokes grep(1) on files which may be either uncompressed or compressed with xz(1), lzma(1), gzip(1),
bzip2(1), or lzop(1). All options specified are passed directly to grep(1).
If no file is specified, then standard input is decompressed if necessary and fed to grep(1). When reading
from standard input, gzip(1), bzip2(1), and lzop(1) compressed files are not supported.
If xzgrep is invoked as xzegrep or xzfgrep then egrep(1) or fgrep(1) is used instead of grep(1). The same
applies to names lzgrep, lzegrep, and lzfgrep, which are provided for backward compatibility with LZMA Utils.