Shell module, Shell.pm, does not seem to run shell commands with Centos 7.4.
For instance following script is OK with Centos 6.4:
#!/usr/bin/perl
use Shell qw(ps);
$cmd=ps;
print $cmd . "\n";
Result is as expected:
PID TTY TIME CMD
29090 pts/1 00:00:00 bash
29325 pts/1 00:00:00 test.pm
29326 pts/1 00:00:00 ps
But with Centos 7.4
#!/usr/bin/perl -I /usr/share/perl5/CPAN
use Shell qw(ps);
$cmd=ps;
print $cmd . "\n";
Result is:
ps
If i add to the previous script:
cat("/etc/passwd");
Following error is raised:
Undefined subroutine &main::cat called at ./test.pm line 10
With a real script none of system commands are well interpreted. Should I rewrite everything with system('command')!?
Finally I succeeded to make it work !
Installation was not quite good.
I had to run :
cpan App::cpanminus
then
cpanm Shell
Related
wsl -h shows the following:
--exec, -e <CommandLine> Execute the specified command without using the default Linux shell.
-- Pass the remaining command line as is.
What does "without using the default Linux shell" mean (i.e. what else is it going to use, if not the default shell!?)?.
Additionally, by way of an example, I now have three possible ways to run Linux ls from my PowerShell prompt (i.e. this will not be Get-ChildItem aliased to ls, but instead a Linux command via WSL):
PS C:\> wsl -e ls # Alternatively, wsl --exec ls
PS C:\> wsl -- ls
PS C:\> wsl ls
But all outputs appear to be the same. How would you explain the differences between these three ways of running a WSL Linux command from a PowerShell prompt?
I think it means wsl runs the command directly, instead of spawning a shell process to run the command.
For example, if I run :
wsl -e sleep 10
From another terminal, I have :
root 1482 1 0 11:32 tty3 00:00:00 /init
ubuntu 1483 1482 0 11:32 tty3 00:00:00 sleep 10
We can see /init is the parent of sleep 10, without a shell in between.
A cool trick is using this to set the X11 $DISPLAY variable, letting you use windows terminal to get remote shells using WSLG.
# in microsoft terminal or powershell use this command line
wsl.exe -- ssh -a -X -Y $hostname
then on the remote system
# DISPLAY will show something like localhost:10.0 on the remote system
echo $DISPLAY
# use a program like xeyes to test
xeyes
I have a bash script that executes in loop a python script:
while true; do python3 script.py && break; done
launched with nohup:
nohup ./run_script.sh &
Why if I run the command:
tail -f nohup.out
I don't see the output of the python script?
I correctly see the script in my running process:
pi 2757 1.5 3.4 37268 33064 ? S 15:06 0:18 python3 script.py
pi 2819 0.0 0.0 1908 388 ? S 15:07 0:00 /bin/sh ./run_script.sh
pi 2820 1.6 3.5 37268 33096 ? S 15:07 0:18 python3 script.py
If I directly launch the python script with nohup, I see the output but I need to relaunch the script everytime it fails, so I need to lauch it with the bash script
Maybe I'm missing some concept concerning nohup usage.
I resolved modifing the script in this way:
while true; do python3 -u script.py && break; done
The output file nohup.out during execution remains empty until the execution is finished. This happens because of output buffering. Adding the -u flag I can avoid output buffering.
For other details see this blog page https://janakiev.com/blog/python-background/.
I have a startup script running on boot in Linx:
/etc/init/selfconfig
#! /bin/sh
# /etc/init.d/selfconfig
USER=root
HOME=/root
export USER HOME
/usr/bin/perl /boot/coder_settings/saconfig.pl
exit 0
this script runs a perl script
/boot/coder_settings/saconfig.pl
#! /usr/bin/perl
lwp-request -m GET http://192.168.1.16:3000/hostname > /boot/coder_settings/hostname.txt
But the I'm getting this error:
Search pattern not terminated at /boot/coder_settings/saconfig.pl line 3.
What am I doing wrong?
Although lwp-request is a perl script, it's setup to run as a command line program.
You can simply change your bash script from;
#! /bin/sh
....
/usr/bin/perl /boot/coder_settings/saconfig.pl
To;
#! /bin/sh
....
lwp-request -m GET http://192.168.1.16:3000/hostname > /boot/coder_settings/hostname.txt
If you want to run lwp-request as a shell command from perl use backticks change your perl script to;
#! /usr/bin/perl
`lwp-request -m GET http://192.168.1.16:3000/hostname > /boot/coder_settings/hostname.txt`
I use a terminal which I don't know the name. By which command can I find the name and version of that?
(I use android operating system)
echo $TERM tells you kind of terminal you are using, eg. xterm
Use the ps command with no arguments to get the processes running under the current shell.
Example:
% ps
PID TTY TIME CMD
1917 pts/0 00:00:00 zsh
13659 pts/0 00:00:00 ps
Let's say I have written a Perl script called "foo.pl" that takes in a password argument via the -p switch.
However, while it is running, anyone can do a ps and see the entire command-line string, including the password:
$ ps a |grep 'foo\.pl'
32310 pts/4 S+ 0:00 /usr/bin/perl -w ./foo.pl -p password
32313 pts/5 S+ 0:00 grep foo.pl
What is the easiest/simplest way to hide the password and replace it with something like xxxxxx?
Ask for the password from inside the script, so you don't have to pass it as an argument.
Update
Apparently this work for me, simulating a mysql behaviour:
#!/usr/bin/perl
($0 = "$0 #ARGV") =~ s/--password=\K\S+/x/;
<STDIN>;
$ ./s --user=me --password=secret
^Z
$ ps
PID TTY TIME CMD
1637 ttys000 0:00.12 -bash
2013 ttys000 0:00.00 ./s --user=me --password=x
Under MacOS 10.6
Passing passwords on the command line is not really a good idea, as already mentioned.
But: you can usually (it is OS-dependent) change the name that is shown by ps by assigning to $0.
e.g. (tested on Linux)
$ cat secret.pl
#!/usr/bin/perl
$0 = "my secret perl script";
sleep 15;
$ ./secret.pl -p foobar &
[2] 426
$ ps a | grep perl
426 pts/0 S 0:00 my secret perl script
428 pts/0 S+ 0:00 grep perl
See the section on $0 in the perlvar manpage for details.
There are a couple of ways to go. The most immediate is to (like sidyll says) prompt for the password in the actual script. Don't put in on the command line, and you won't have to hide it.
Another option is a private password file. This file can be read through shell interpolation, but it's still kind of a kludge.
You could add a bit more flexibility to the private password file by wrapping your script in a "launcher" script. Essentially, you write a script whose sole purpose is to "set up" the password file, and then launch your real script.