3 ms·
> For example, grep and egrep are two commands that perform very similar functions and are therefore implemented as a single program. Not everywhere: $ ls
by _kst_ 10y ago
> For example, grep and egrep are two commands that perform very similar functions and are therefore implemented as a single program.
Not everywhere:
$ ls -li /bin/grep /bin/egrep /bin/fgrep
37748784 -rwxr-xr-x 1 root root 183696 Jan 18 2014 /bin/egrep
37748788 -rwxr-xr-x 1 root root 138352 Jan 18 2014 /bin/fgrep
37748794 -rwxr-xr-x 1 root root 191952 Jan 18 2014 /bin/grep
(That's on Ubuntu 14.04.)
- MustardTiger 10y agoHe's an openbsd developer, he's posting about openbsd. Hence the talk of how things got to be into older BSD systems and made their way to openbsd.
- rraval 10y agoThat may just be because they are shell scripts instead of symlinks. On ArchLinux: $ ls -li /usr/bin/{grep,egrep,fgrep} 1728040 -rwxr-xr-x 1 root root 28 Apr 23 12:12 /usr/bin/egrep* 1728041 -rwxr-xr-x 1 root root 28 Apr 23 12:12 /usr/bin/fgrep* 1728042 -rwxr-xr-x 1 root root 159024 Apr 23 12:12 /usr/bin/grep* $ cat /usr/bin/egrep #!/bin/sh exec grep -E "$@" $ cat /usr/bin/fgrep #!/bin/sh exec grep -F "$@" The general point of them being implemented by the same executable still stands.
- _kst_ 10y agoNo, on my system they're three distinct executables; check the sizes shown in my previous comment. Ubuntu 14.04 uses GNU grep 2.16. When I install it from source (grep-2.16.tar.xz), I get the three distinct executables. When I install the latest version (2.25) from source, egrep and fgrep are shell script that invoke "grep". (Which could be a problem if you happen to have another "grep" command in an earlier directory in your $PATH. Symlinks would avoid that problem.) Here's the Changelog entry for the change to shell scripts: 2014-03-23 Paul Eggert <eggert@cs.ucla.edu> egrep, fgrep: go back to shell scripts Although egrep's and fgrep's switch from shell scripts to executables may have made sense in 2005, it complicated maintenance and recently has caused subtle performance bugs. Go back to the old way of doing things, as it's simpler and more easily separated from the mainstream implementation. This should be good enough nowadays, as POSIX has withdrawn egrep/fgrep and portable applications should be using -E/-F anyway.
- Tiksi 10y agoJust as another data point, on my system (fully up to date arch) it's half and half: $ file -i /usr/bin/*grep|sort -k2,2 [17:59:42] /usr/bin/grep: application/x-executable; charset=binary /usr/bin/igrep: application/x-executable; charset=binary /usr/bin/pgrep: application/x-executable; charset=binary /usr/bin/msggrep: application/x-executable; charset=binary /usr/bin/deepgrep: application/x-executable; charset=binary /usr/bin/pcregrep: application/x-executable; charset=binary /usr/bin/lzgrep: inode/symlink; charset=binary /usr/bin/lzegrep: inode/symlink; charset=binary /usr/bin/lzfgrep: inode/symlink; charset=binary /usr/bin/xzegrep: inode/symlink; charset=binary /usr/bin/xzfgrep: inode/symlink; charset=binary /usr/bin/egrep: text/x-shellscript; charset=us-ascii /usr/bin/fgrep: text/x-shellscript; charset=us-ascii /usr/bin/zgrep: text/x-shellscript; charset=us-ascii /usr/bin/bzgrep: text/x-shellscript; charset=us-ascii /usr/bin/xzgrep: text/x-shellscript; charset=us-ascii /usr/bin/zegrep: text/x-shellscript; charset=us-ascii /usr/bin/zfgrep: text/x-shellscript; charset=us-ascii /usr/bin/zipgrep: text/x-shellscript; charset=us-ascii