help with grep [[:alpha:]]* -o

Question

file.txt contains:

##w##

##wew##

using mac 10.6, bash shell, the command:

cat file.txt | grep [[:alpha:]]* -o

outputs nothing. I'm trying to extract the text inside the hash signs. What am i doing wrong?

Answer 1

(Note that it is better practice in this instance to pass the filename as an argument to grep instead of piping the output of cat to grep: grep PATTERN file instead of cat file | grep PATTERN.)

What shell are you using to execute this command? I suspect that your problem is that the shell is interpreting the asterisk as a wildcard and trying to glob files.

Try quoting your pattern, e.g. grep '[[:alpha:]]*' -o file.txt.

I've noticed that this works fine with the version of grep that's on my Linux machine, but the grep on my Mac requires the command grep -E '[[:alpha:]]+' -o file.txt.

Answer 2

sed 's/#//g' file.txt

/SCRIPTS [31]> cat file.txt
##w##
##wew##

/SCRIPTS [32]>  sed 's/#//g' file.txt
w
wew

Answer 3

if you have bash >3.1

while read -r line
do
  case "$line" in
   *"#"* )
        if [[ $line =~ "^#+(.*)##+$" ]];then
            echo ${BASH_REMATCH[1]}
        fi
  esac    
done <"file"