This has be stump. I wrote a shell program in C that allows the user to execute several commands. Based on my research so far, all the commands such as "ls" and "cat" are located in "/bin/".
The "wc" is not listed in this directory - "/bin". If I fire up a terminal, I can type "wc fileName" and it works. I ran "find . wc" from the "/" directory, and I still can't find the "wc" command.
Does anyone know where "wc" is hiding?
Try typing which wc into your shell...that should tell you where it is.
On my machine it is in /bin/.
However, if you just want the path resolution to be done on it's own, you can use the system() function (see man 3 system for more information). As you can read in the documentation, that's really the same as invoking the Bourne shell (or wherever the symlink for that points to) for the path resolution, so if you don't want that overhead, you will want to stick with whatever method you are currently using.
I tried whereis wc and I get it in /usr/bin/wc
If you don't want to worry about where individual utilities are, but you do want to avoid the overhead involved in calling system, then you should try the middle-level function execvp, or one of its friends (also listed on that page). Sadly, there is no execvpe.
You can try whence, which, or whereis to find any program in your exec path, depending on which shell you're using.
Utilities like wc are usually located in /binor /usr/bin, or in places like /usr/local/bin or /usr/site/bin.
Related
I've recently started using fish, and I needed to use a jar file for google's bundletool.
As such, I needed to set up an alias/function for bundletool, and I chose a function since it seems more "fishy".
My function is simple:
function bundletool
java -jar bundletool-all-1.12.1.jar $argv
end
The bundletool jar itself lives at ~/.local/bin, which is on my fish user path:
lase#laser-razer /m/c/U/matth [1]> echo $fish_user_paths
/home/lase/.local/bin /usr/local/go/bin /home/lase/.nvm /home/lase/.cargo/bin /home/lase/.cargo
In a regular shell, I can execute java -jar bundletool-all-1.12.1.jar, and the command runs as expected. However, in the function, fish doesn't seem to know about my fish_user_paths, and reports it cannot find the jar file.
To remedy this, I had to update my function to specify the full path:
function bundletool
java -jar ~/.local/bin/bundletool-all-1.12.1.jar $argv
end
This works, but I feel like I'm doing something incorrectly. Should I be setting up my paths or functions in a different fashion?
Your function will run in the ordinary environment.
It will run with the current $PATH [0] and, more importantly to you, the current working directory.
What happens is this:
java -jar bundletool-all-1.12.1.jar
Will tell java to run the jar found at bundletool-all-1.12.1.jar.
Notably, fish just hands java the string "bundletool-all-1.12.1.jar", and java will then not look at $PATH. It does not care about $PATH. It simply looks at "bundletool-all-1.12.1.jar", and tries to open a file by that name.
And it will find that file, if it is in the current directory.
And that's the reason this worked for you when you executed it interactively - because you happened to be in that directory
And then you tried it with the function, but you tried it from a different directory, and so it didn't work.
This works, but I feel like I'm doing something incorrectly. Should I be setting up my paths or functions in a different fashion?
No, giving the full path to the file instead of relying on the working directory is the right thing to do.
[0]: $fish_user_paths is just a variable you set, that fish will then take care to add to $PATH. $PATH is the actual variable that fish and other tools (including any command fish starts, if it wants to) will use to find commands.
I call the program myfoo.pl, my first line is #!/usr/bin/perl.
When run from command line myfoo.pl I get command not found.
again when run using perl myfoo.pl it runs and completes. Not all my perl programs have this problem some run just using (path)/source.pl I ran head -1 myfoo.pl and got a print of my first line. no indication of problems.
Looking at the limited information you gave, I would say you are probably missing permission executable on the file myfoo.pl. To which the solution is to do
chmod +x myfoo.pl
It could also be a path to binary problem, that the perl binary is not located in /usr/bin/perl. In which case you need to figure out where it is, with which perl or where perl.
I suppose it could also be that the file myfoo.pl is not in your current directory, which it needs to be. Because of path settings, you also may have to execute it with
$ ./myfoo.pl
Because . is part of your path variable.
It is impossible to say for sure, because you are not answering questions, however. So when you eventually get around to answering questions, we may have more answers.
I am new in Perl. I am using the following command to remove a folder in Perl, under Windows:
system "del trash_folder";
But I intend to run the same script under Unix as well. I could get the OS name in the code and run a different command based on the OS. But is there no better way in Perl? I am thinking of possibly an API or so that is OS-ignorant.
The del command is never going to create a new directory, is it? :-)
If you want to create directories, use the mkdir command.
If you want to remove directories, use the rmdir command.
Update: In general, if you have a choice between using a Perl built-in function or an external command, then the Perl function will be the better choice. Firstly, your code will be more portable and, secondly, opening a sub-shell to run the external command will slow your program down.
I have this perl script that I need to distribute to my coworkers who want to run the script from anywhere in the unix environment. What can I do on my part to make running this PERL script easy for them? For example, they can just have the PERL script somewhere in their directory and run just typing
./xyz.pl ttt.conf
with no path declared (like /home/abc/bin/ddd/xyz.pl ttt.conf).
The way I used to do it is add a "bin" directory in your home directory, and add it to the $PATH variable.. then you can add any script you want to use to that directory.
I am no longer familiar with the exact syntax, but something like:
in .bashrc:
$PATH = ( $PATH , $HOME/bin )
Then place the script in /home/user/bin (assuming $HOME == /home/user). When you reload the shell, it will be usable like any normal command/program.
ETA: See robert's comment below on syntax. Also, to allow your co-workers to use a script of yours, you can simply use a hard-coded path, such as /home/patrick/bin.
Put the script in /usr/local/bin (or anywhere else in $PATH). Your sysadmin may have to help you.
The technique I use is:
#!/usr/bin/env perl
This is a common way of getting the command interpreter to find Perl without either (a) moving the file, or (b) declaring the explicit path for Perl in the shebang.
It's mentioned under portability at: http://en.wikipedia.org/wiki/Shebang_(Unix)
You all are kind of right... but that perl script can sit in your path till the cows come home... and it ain't gonna run... until you set the executable bit....
:bin localadmin$ ./perlextip
-bash: ./perlextip: Permission denied
:bin localadmin$ chmod +x perlextip
:bin localadmin$ ./perlextip
Exit 0! Yeehaw.
Also, it should be noted that it need not be IN your path.... You can just call it by the full path, preceeded with a period and a slash, to execute it..
:/ localadmin$ ./ServiceData/UNIX/bin/extip
Exit 0! Yeehaw.
You can also create an alias for such a command in your ~/.bash_profile, or the such, which will let you make a system-wide shortcut of sorts, and you can even throw in a sudo, or the like, if you were so inclined... Then just call that "extip" by name anywhere, you'll be prompted for a password and, all will be well in the world.
alias extip='sudo ./ServiceData/UNIX/bin/extip'
In bash, executables such as mplayer and imagemagick's "convert" have a cool auto-complete functionality on their command line arguments. For instance, if I type
mplayer <tab><tab>
in one of my video folders, then mplayer will list all media files located in that folder, and only the media files.
Similarly, if I type
convert -<tab><tab>
then I will see all the possible options of the convert script, which is great.
My question is how to achieve a similar functionality, using bash, ruby or python scripts?
This is an example of BASH's smart completion. A basic description is here, a guide to writing your own extensions is here and another (Debian-based) guide is here. And here's a fuller featured introduction to the complete command (the command that facilitates this behaviour).
The link to writing your own extension in the accepted answer has gone dead. Quoting here from http://web.archive.org/web/20090409201619/http://ifacethoughts.net/2009/04/06/extending-bash-auto-completion/
Bash provides you a way of specifying your keywords, and using them to
auto complete command line arguments for your application. I use vim
as a wiki, task managemer and contacts. The vim helptags system lets
me index the content instead of searching through it, and the speed
shows it. One feature I wanted to add to this was to access these tags
from outside vim.
This can be done in a straight forward way:
$ vim -t tagname
This takes me directly to specific content marked using this tag. However, this will be more productive if I can provide
auto-completion for the tags.
I first defined a Bash function for the vim commandline. I added the
following code to my .bashrc file:
function get {
vim -t $1
} Now I can use get tagname command to get to the content.
Bash programmable completion is done by sourcing the
/etc/bash-completion script. The script lets us add our
auto-completion script /etc/bash-completion.d/ directory and executes
it whenever it is called. So I added a script file called get with the
following code in that directory.
_get()
{
local cur
COMPREPLY=()
#Variable to hold the current word
cur="${COMP_WORDS[COMP_CWORD]}"
#Build a list of our keywords for auto-completion using
#the tags file
local tags=$(for t in `cat /home/anadgouda/wiki/tags | \
awk '{print $1}'`; do echo ${t}; done)
#Generate possible matches and store them in the
#array variable COMPREPLY
COMPREPLY=($(compgen -W "${tags}" $cur))
}
#Assign the auto-completion function _get for our command get.
complete -F _get get Once the /etc/bash-completion is sourced, you will get auto-completion for the tags when you use the get command.
Along with my wiki I use it for all the documentation work and at
times the code too. I also use the tags file created from my code. The
indexing system lets me remember the context instead of the filenames
and directories.
You can tweak this system for any of the tools you use. All you need
to do is get a list of the keywords for your command and give it to
the Bash programmable completion system.
This functionality in bash is provided by bash-completion and similar functionality is included in zsh. If you want to add support for some program not currently supported by one of these tools, you need to write your own extensions for them.
How do I enable bash completion on Ubuntu?
sudo apt-get install bash-completion
source /etc/profile.d/bash_completion.sh
sudo apt i[TAB]