Hi, > grep 2.5.4 has an undocumented \S operator:
It means it doesn't be supported by grep 2.5.4. Grep 2.5.4 uses regex, which is included in GNU libc and supports `\S' operand. However, Grep 2.5.4 also use own engines, which can't interpret `\S' operand. So you mayn't use undocumented operands.
