How to match any non white space character except a particular one?

Question

You can use a character class:

/[^\s\\]/

matches anything that is not a whitespace character nor a \. Here's another example:

[abc] means "match a, b or c"; [^abc] means "match any character except a, b or c".

You can use a lookahead:

/(?=\S)[^\\]/

This worked for me using sed [Edit: comment below points out sed doesn't support \s]

[^ ]

while

[^\s] 

didn't

# Delete everything except space and 'g'
echo "ghai ghai" | sed "s/[^\sg]//g"
gg

echo "ghai ghai" | sed "s/[^ g]//g"
g g

On my system: CentOS 5

I can use \s outside of collections but have to use [:space:] inside of collections. In fact I can use [:space:] only inside collections. So to match a single space using this I have to use [[:space:]] Which is really strange.

echo a b cX | sed -r "s/(a\sb[[:space:]]c[^[:space:]])/Result: \1/"

Result: a b cX

• first space I match with \s
• second space I match alternatively with [[:space:]]
• the X I match with "all but no space" [^[:space:]]

These two will not work:

a[:space:]b  instead use a\sb or a[[:space:]]b

a[^\s]b      instead use a[^[:space:]]b