For example, the following command lists all the options in the kernel config file:
busybox grep -o "CONFIG_[^=]*" /usr/src/linux/.config
I did some brief testing and found one issue compared to GNU grep (2.5.1): when -o is used in combination with -v, the modified busybox grep will print empty lines whereas GNU grep prints nothing. When -o is used with -v and -n, the modified busybox grep prints line numbers followed by line feeds, whereas GNU grep prints line numbers in a long stream without line feeds. However the usage of -o in combination with -v is so unlikely that I don't think it's worth fixing.
For example: when running this command:
grep -ov CONFIG /usr/src/linux/.config
GNU grep will produce no output, busybox produces a lot of empty lines. Another example: when running this command:
grep -ovn CONFIG /usr/src/linux/.config
GNU grep will produce a long list of line numbers in one stream:
1:2:3:4:5: ... (etc)
Busybox produces a lot of empty lines with line numbers:
1:
2:
3:
4:
5:
... (etc)
A pretty simple patch that has helped me in my project which is to build a uClibc/BusyBox-based install of Gentoo. Gentoo's rc scripts use grep -o in a lot of places and it was really a lot easier to modify the grep.c code than to manually replace all the occurrences of grep -o by something like sed -n "s/something\(${1}\)something/\1/gp".
- Added 'o' to GREP_OPTS, added GREP_OPT_o macro to correspond to it and modified all other GREP_OPT_? macros to accomodate for the change
- Added declaration of regmatch_t regmatch to grep_file(), modified the call to regexec so it uses regmatch; regmatch's contents have to be reset before _each_ regexec call because regexec doesn't change regmatch if there's no match, this would give trouble when using -v option.
- Put an "if" around the print_line call in grep_file() so when -o is used, the program only prints the part of the line that matches the (first occurrence of the) regular expression.
- Modified initialization of reflags static variable so that the REG_NOSUB flag is not set when -o is used (when REG_NOSUB is set, regexec ignores the regmatch parameters).
Use the patch in any way you find useful. I will be happy to help if you find a problem. The patch doesn't include a change to the documentation or test code. Let me know if you need help with that. I did some brief testing on various combinations of -o with other options but my testing was not exhaustive; if you find any anomalies and want me to fix it, let me know.
Thanks for reading!
grep-o.patch [^] (3,015 bytes) 08-16-06 15:53 
