I want to grep variable pattern which is in first column.
$ cat test.txt
abc.xyz
abc.def
pqr.tap
pqr.abc
abc.mnp
mnp.abc
abc.pqr
abc.mob
If variable pattern is abc then output should be
abc.xyz
abc.def
abc.mnp
abc.pqr
abc.mob
If variable pattern is mnp then output should be
mnp.abc
If pattern is not variable then I can do by command (For pattern mnp)
awk -F"." '{ if($1 == "mnp") print $0;}' test.txt
Lets say:
pt="abc"
awk -v variable="$pt" -F"." '$1 ~ variable {print $0}' test.txt
More of this here
variable is an awk variable for which a shell variable pt was assigned. With filed separator . we get $1 and compare it with variable and if it matches it prints the whole line.from the file test.txt. As for why to use awk variable, refer the aforementioned link.
If you always have the same line format you can simply grep "abc." (or whatever before the point including the point):
grep abc. file.txt
grep '^abc'orawk '/^abc/'