4.10. How do I perform a case-insensitive search?
Several versions of sed support case-insensitive matching: ssed and
GNU sed v3.02+ (with I flag after s/// or /regex/); sedmod with the
-i switch; and sed16 (which supports both types of switches).
With other versions of sed, case-insensitive searching is awkward,
so people may use awk or perl instead, since these programs have
options for case-insensitive searches. In gawk/mawk, use "BEGIN
{IGNORECASE=1}" and in perl, "/regex/i". For other seds, here are
three solutions:
Solution 1: convert everything to upper case and search normally
# sed script, solution 1
h; # copy the original line to the hold space
# convert the pattern space to solid caps
y/abcdefghijklmnopqrstuvwxyz/ABCDEFGHIJKLMNOPQRSTUVWXYZ/
# now we can search for the word "CARLOS"
/CARLOS/ {
# add or insert lines. Note: "s/.../.../" will not work
# here because we are searching a modified pattern
# space and are not printing the pattern space.
}
x; # get back the original pattern space
# the original pattern space will be printed
#---end of sed script---
Solution 2: search for both cases
Often, proper names will either start with all lower-case ("unix"),
with an initial capital letter ("Unix") or occur in solid caps
("UNIX"). There may be no need to search for every possibility.
/UNIX/b match
/[Uu]nix/b match
Solution 3: search for all possible cases
# If you must, search for any possible combination
/[Ca][Aa][Rr][Ll][Oo][Ss]/ { ... }
Bear in mind that as the pattern length increases, this solution
becomes an order of magnitude slower than the one of Solution 1, at
least with some implementations of sed.
