Hi all, after I save the attached file as 1.dat , I see that grep -iP on '^Subject:' or on '^S' gets stuck in the en_US.UTF-8 locale. It is fine in pcregrep and in ack. [SHELL] shlomif@telaviv1:~$ time LC_ALL=en_US.UTF-8 ~/apps/TEST-grep-from-git-TO-DEL/bin/grep -iP '^Subject:' < 1.dat ^C real 0m4.199s user 0m4.195s sys 0m0.003s shlomif@telaviv1:~$ time LC_ALL=en_US.UTF-8 ~/apps/TEST-grep-from-git-TO-DEL/bin/grep -iP '^S' < 1.dat ^C real 0m3.486s user 0m3.485s sys 0m0.001s shlomif@telaviv1:~$ time LC_ALL=en_US.UTF-8 ~/apps/TEST-grep-from-git-TO-DEL/bin/grep -iE '^S' < 1.dat real 0m0.002s user 0m0.002s sys 0m0.000s shlomif@telaviv1:~$ time LC_ALL=en_US.UTF-8 ~/apps/TEST-grep-from-git-TO-DEL/bin/grep -P '^S' < 1.dat ^C real 0m1.887s user 0m1.885s sys 0m0.000s shlomif@telaviv1:~$ time LC_ALL=en_US.UTF-8 ~/apps/TEST-grep-from-git-TO-DEL/bin/grep -P '^Subject:' < 1.dat real 0m0.003s user 0m0.000s sys 0m0.002s shlomif@telaviv1:~$ time LC_ALL=en_US.UTF-8 ~/apps/TEST-grep-from-git-TO-DEL/bin/grep -P '^Subject:' < 1.dat time LC_ALL=C ~/apps/TEST-grep-from-git-TO-DEL/bin/grep -iP '^Subject:' < 1.dat real 0m0.003s user 0m0.001s sys 0m0.001s shlomif@telaviv1:~$ time LC_ALL=C pcregrep -i '^Subject:' < 1.dat real 0m0.002s user 0m0.001s sys 0m0.000s shlomif@telaviv1:~$ time LC_ALL=C ack -i '^Subject:' 1.dat real 0m0.066s user 0m0.059s sys 0m0.007s shlomif@telaviv1:~$ time LC_ALL=en_US.UTF-8 ack -i '^Subject:' 1.dat real 0m0.070s user 0m0.063s sys 0m0.006s [/SHELL] The same thing happens with grep-2.16 built from the sources. I'm on Mageia Linux x86-64 Cauldron (what will be Mageia 4). shlomif@telaviv1:~$ ldd ~/apps/TEST-grep-from-git-TO-DEL/bin/grep linux-vdso.so.1 (0x00007fff2a7fe000) libpcre.so.1 => /lib64/libpcre.so.1 (0x00007f19ed302000) libc.so.6 => /lib64/libc.so.6 (0x00007f19ecf4d000) libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f19ecd30000) /lib64/ld-linux-x86-64.so.2 (0x00007f19ed568000) shlomif@telaviv1:~$ rpm -qf /lib64/libpcre.so.1 lib64pcre1-8.33-2.mga4 Regards, Shlomi Fish -- ----------------------------------------------------------------- Shlomi Fish http://www.shlomifish.org/ Humanity - Parody of Modern Life - http://shlom.in/humanity Linux — Because Software Problems Should not Cost Money. Please reply to list if it's a mailing list post - http://shlom.in/reply .