Grep for variable hex value

user_1950053 0
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I am trying to count the number of times a hex value appears in a file. The hex value is set in a variable.

Using the literal string "x01" returns the correct count:

grep -o $'\x01' ${fileName} | wc -l

How can I use a variable in place of x01 ?

grep bash
1 Answers

Borrowing from Conversion hex string into ascii in bash command line

# single quote character in hex
$ a='\x27'

$ echo "a'b'c" | grep -o $(echo "$a" | xxd -r -p)
'
'

$ echo "a'b'c" | grep -o $(echo "$a" | xxd -r -p) | wc -l
2

# you can also use just the number, \x prefix is optional
$ echo "a'b'c" | grep -o $(echo '27' | xxd -r -p) | wc -l
2

# if PCRE is available
$ echo "a'b'c" | grep -oP "$a" | wc -l
2

# with ripgrep (https://github.com/BurntSushi/ripgrep)
$ echo "a'b'c" | rg -oc "$a"
2
user_40820520
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