Hi i have a file containing the following:
7 Y-N2 8 Y-H 9 Y-O2 I want to match it with the following sed command and get the number at the beginning of the line:
abc=$(sed -n -E "s/([0-9]*)(^[a-zA-Z])($j)/\1/g" file) $j is a variable and contains exactly Y-O2 or Y-H.
The Number is not the linenumber.
The Number is always followed by a Letter.
Before the Number are Whitespaces.
echoing $abc returns a whiteline.
Thanks
many problems here:
^ must be inside the char class to make a negative letter-n option, so you must use p command or nothing will ever be printed (and the g option is useless here)working command (I have changed -E by -n because it was unsupported by my sed version, both should work):
sed -nr "s/ *([0-9]+) +([^a-zA-Z])($j)/\1/p" file Note: awk seems more suited for the job. Ex:
awk -v j=$j '$2 == j { print $1 }' file 
Sed seems to be overly complex for this task, but with awk you can write:
awk -vk="$var" '$2==k{print $1}' file With -vk="$var" we set the awk variable k to the value of the $var shell variable.
Then, we use the 'filter{command}' syntax, where the filter $2==k is that the second field is equal to the variable k. If we have a match, we print the first field with {print $1}.
Try this:
abc=$(sed -n "s/^ *\([0-9]*\) *Y-[OH]2*.*/\1/p" file) Explanations:
^ *: in lines starting with any number of spaces\([0-9]*\): following number are captured using backreference*: after any number of spacesY-[OH]2*: search for Y- string followed by N or H with optional 2\1/p: captured string \1 is output with p command
awk -vk="$var" '$2==k{print $1}' file