Today I discovered you can make less act like tail -f.
less filename, then press Shift-F to start follow mode.
Just like tail, but you have all the added features of less - like scrolling, searching, and the highlighting of search hits.
I've been watching log files with tail for years.
This just made me ponder: are there other commands that are outdated and have powerful alternatives?
Please share the bliss - a single command per post.
One might say that awk has been completely obsoleted by perl.
However, since I was using awk since before perl existed, I still use it; as for more serious scripts, I use python instead of perl.
'rename' is a good alternative to the long oneliners one writes to change name to a bunch of files.
I like to point to my ack, an alternative to grep for programmers.
I'm surprised people (including me) have lived with cobbled-together aliases and shell scripts with find & xargs for so long.
It's worth having a look at the GNU versions of some commonplace commands, since they've quietly acquired useful refinements beyond the standard (XPG4, etc.) versions.
For example, recursive grep is much nicer than find | xargs grep.
Also, find ... -print0 | xargs -0 ... handles the long-standing horrible quoting problem that makes xargs fail to handle funky space-filled filenames properly.
GNU tar takes 'j' and 'z' flags to handle bzipped and gzipped archives directly.
And bash's $() alternative to backticks makes the occasional nested backquoted expression easier to read and write.
pax is a replacement for tar and cpio, with a sane set of command-line options: -r to read from an archive, -w to write to an archive, -rw to do tree-to-tree copies. It also provides a -s option to allow you to perform substitutions on filenames before reading/writing a file from/to an archive. :-)
Edit: Mark Baker makes an interesting point (in comments) that I should clarify. pax makes pax archives (which are an extension of ustar, and can be unpacked by most tar programs) by default. But, with the -x option, it can be made to create cpio archives and ustar archives (these two are guaranteed by the standard). Some implementations, such as the BSD one, support creating even more types, such as old-style (pre-ustar) tar archives.
Not exactly replacements for anything, but moreutils is a collection of small Unixy tools, which are basically meant to fill holes in the *nix toolbox.
Since, you only wanted one command per post, I guess I'll have to choose sponge, which allows you to save the output of a pipe to one of the files used as input. IOW, it allows you to modify files in-place, without having to worry about temporary files.
For example, if you do:
grep 'something' somefile.txt > somefile.txt
somefile.txt will end up empty. So, you could use sponge:
grep 'something' somefile.txt | sponge somefile.txt
Not really a replacement for an outdated command per se, but screen is a great alternative to opening multiple terminal windows and/or using bg, etc.
bm (link), instead of popd and pushd or creating temporary aliases, is really useful.
To add a directory to be called with tag
bm -a /path/to/a/dir tag
To go to this directory
cdbm tag
If you're on a GNU system, don't use sed '1!G;h;$!d'; instead, use tac.
On Linux, ip (from the iproute2 package) behaves more predictably and gives easier-to-parse output than ifconfig/route.
Wherever glibc is installed, you can getent passwd foo instead of grep foo /etc/passwd (similarly for aliases ethers group hosts netgroup networks protocols rpc services shadow) -- it even Does The Right Thing(TM) in an NIS setup.
Why bother typing gzip -dc foo.tar.gz | tar xf - when tar xzf foo.tar.gz will spawn the decompressor for you?
Going even further... why bother typing tar xzf foo.tar.gz or tar xjf foo.tar.bz2 when GNUtar will automatically detect compression? tar xf foo.tar.(gz|bz2) just magically works.
The question and tags are contradictory. Linux isn't Unix (stupid Open Group), and most "real" Unix boxes don't have anywhere close to the software that Linux does. As an example, on a fairly plain AIX 5.3pl6 install:
$ less ksh: less: not found.
And yes, I admin these systems, but we've agreed to not load non-core components in most cases since we need them to match the deployed systems in the field.
It's great to have the newer tools in your toolbox, but if you don't know the "old school" way then you're going to be in a world of hurt if you're ever on a AIX/Solaris/HP-UX/etc system which doesn't have the newer tools (and may not even have bash).
Note, on our development VM I do have as many modern tools installed as I can find, simply because while I can work in a more plain environment, it doesn't mean that I enjoy it. And I do as much work as possible on our Linux (CentOS 5) system, simply because the tools on it are still newer than anything I can find readily packaged for AIX (Solaris is somewhat better; HP-UX is infinitely worse).
ar(1) archives; tar is almost always used instead. ar does continue to have some limited uses; .deb package files are actually ar archives, for example, and the .a library libraries used for static compilation are actually ar archives containing a bunch of .o object files.
Essentially, in the few places where ar is used, its existence is hidden away.
compress -- replaced by gzip (even available on traditional Unix systems by default now). It can handle .Z files. More importantly, gzip is faster and creates smaller output than compress.
Context sensitive autocompletion.
Well, I know, it's not a command and it's unlikely to be found on many Unices, but Linux. In my Ubuntu Hardy, bash_completion is already configured very well, and that means not only for files and direcotires! For example if I type
svn pr<TAB><TAB>
I get:
praise propdel propedit propget proplist propset
And even
svn propget svn:k<TAB>
I get automaticaly
svn propget svn:keywords
It works also for ant and make automatically reading the default files or the ones specified on the commandline! That's a real time saver!
I'm not sure if this should be an answer or merely an edit to the question.
Before using less as a tail replacement, you can search for something "/search_string" and THEN invoke the Follow command (shift-F). Now any "search_strings" that scroll by will be highlighted. This is useful for when you're scanning a bunch of program output or logs and are looking for a particular string or pattern.
Don't forget that you can use regular expressions, too!
But, less is still no replacement for 'tail -f'. If you need to filter a log in realtime for a live test, less won't beat 'tail -f | grep xxxxx'.
I agree with MadCoder that `tail -f' allows you to connect things using a pipe while less cannot. But less is easier for interactive sessions, which is what it is designed for. So strictly speaking this is not a replacement.
But other things may be. For example, vim replaced vi and ed virtually everywhere in the PC world, nano replaces pico (not because it's better but because it's free), mutt and pine basically replaced things like `mail' in many places. Bash is now dominant and replaced sh. The list can go on and on forever :)
Not sure if it's a perfect replacement but "xtail" is a really nice improvement on "tail".
It can monitor multiple files at the same time. Hitting the interrupt key (commonly CTRL+C) will give you a summary of which files changed by how much.
cfdisk is an easy-to-use upgrade of the command-line drive partitioning utility fdisk.
atool: handling archives without headaches
Some examples:
- aunpack archive.tgz Unpacks all the files in the archive. If the author of the archive was so inconsiderate as to put multiple files in the archive’s root, the command automatically creates a directory and moves the files inside.
- aunpack -e archive1.tgz archive2.zip Unpacks each archive.
- apack archive.tar.bz2 *.txt Creates a new compressed archive containing all text files in the current working directory.
- als archive.rar Shows the names of the files contained in the archive.
Examples are from: http://debaday.debian.net/2008/12/28/atool-handling-archives-without-headaches/
I really like locate as a substitute for find - much easier to use "locate filepattern" than "find / -name filepattern -print", and more efficient because it uses an index database.
You have to have the updatedb command run on a schedule to update the locate database; check your distro's man page for details.
mtr is a traceroute replacement (it is a combination ping and traceroute).
Unlike traceroute, it finds the route almost immediately (since it doesn't wait for a response before moving to the next hop).
The command line version is installed by default in Debian (package mtr-tiny).
innotail
Like tail, but uses the inotify file change notification instead of polling the filesystem. It makes the scrolling look smoother.
I don't know if this qualifies as "outdated," but in my opinion awk makes sed utterly redundant.
ifconfig and iwconfig are deprecated in favor of ip which is a extremely powerful tool to show / manipulate routing, devices, policy routing and tunnels.