bash 问题中的 Sed 正则表达式

Question

Can someone tell me why this sed below doesn't work

...| sed -E $'s/^\d/blah/g'

vs this one works?

| sed -E $'s/^/blah/g'

sample:

echo "10/30/18 04:45:13 PM EDT" | sed -E $'s/^/blah/'

Updated desire:

echo "10/30/18 04:45:13 PM EDT" | 
sed 's/^[[:digit:]][[:digit:]]\/[[:digit:]][[:digit:]]\/[[:digit:]][[:digit:]]/\blah\n/'

blah
10/30/18 04:45:13 PM EDT

Answer 1

Property \\d (digits) works in PCRE/Perl but not in BRE or ERE flavors that is used by sed .

Use [[:digit:]] instead of \\d in sed :

sed 's/^[[:digit:]]/blah/'

---

For your updated question use this gnu sed command:

echo "10/30/18 04:45:13 PM EDT" |
sed -E 's~^([[:digit:]]{2}/){2}[[:digit:]]{2}~\blah\n&~'

blah
10/30/18 04:45:13 PM EDT

Answer 2

This might work for you (GNU sed):

sed '/^..\/..\/.. ..:..:.. /iblah' file

Inserts blah above the regexp and:

sed '/^..\/..\/.. ..:..:.. /ablah' file

Appends blah below the regexp.