I have 2 files. names1.txt and names2.txt.
I need to know that which names are present in names1.txt but are missing in names2.txt. Then I need to store them in another file missing_names.txt.
Diff command gives the difference but it also prints lot many information. Also, I do not want to know the names which are in names2.txt but are missing in names1.txt. So its like (names1.txt - names2.txt) operation.
diff <(sort -u names2.txt) <(sort -u names1.txt) |
sed -n -e 's/^> //p' > missing_names.txt
or
diff <(sort -u names1.txt) <(sort -u names2.txt) |
sed -n -e 's/^< //p' > missing_names.txt
Either of those will give you ONLY the names that are in names1 but not names2.
diff (without any output-format options like -u) prints additions prefixed with > (> followed by a space) and deletions prefixed by < (< followed by a space). The sed scripts strip those from the beginning of the line if they're there and only prints modified (i.e. matching) lines.
sort -u the input files....but what do you mean by "sorting is combining few of the line"? sort doesn't combine lines. it sorts its input, and that's all it does.
cat name_1.txt | while read line
do
grep -q "$line" name_2.txt
if [ "$?" -gt "0" ]; then
echo "$line" >> name_3.txt
fi
done
NOTE: Assuming name_1.txt and name_2.txt contains only names.
-q is used for silent. You can use above code snipped by removing -q as well.
-q for quiet (no output), use grep "$line" name_2.txt > /dev/null. Also, the grep and the if lines can be combined into if ! grep -q "$line" name_2.txt ; then. Or get rid of the if entirely and use ||: grep -q "$line" name_2.txt || echo "$line" >> name_3.txt
man comm.