i'm running a script from ASP.NET/C# using SharpSsh. I realize when the script runs and i do a ps -ef grep from unix, i see the same script running twice, one in csh -c, and the other with ksh. The script has shebang ksh, so i'm not sure why a copy of csh is also running. Also if i run the same script directly from unix, only one copy runs with ksh. There's no other shell running from within the script.
Most Unix/Linux now have a command or option that will show process trees, with indented list like, look for -t or -T options to ps OR ptree OR ???
USER PID PPID START TT TIME CMD
daemon 1 1 11-03-06 ? 0 init
myusr 221568 1 11-03-07 tty10 1.00s \_ -ksh
myusr 350976 221568 07:52:11 tty10 0 | \_ ps -efT
I bet you'll see that the csh is the user login shell that includes your script as an argument ( you may have to use different options to ps to see the full command-line of the csh process) AND as a sub process you'll see ksh executing your script, and further sub-processes under ksh for any external commands that the script is calling.
I hope this helps.
P.S. as you appear to be a new user, if you get an answer that helps you please remember to mark it as accepted, or give it a + (or -) as a useful answer.
Related
I've got a script on my computer named test.py. What I've been doing so far to run the program is type python test.py into the terminal.
Is there a command on Unix operating systems that doesn't require the user to specify the program he/she uses to run the script but that will instead run the script using whichever program the shebang line is pointing to?
For example, I'm looking for a command that would let me type some_command test.txtinto the terminal, and if the first line of test.txt is #!/usr/bin/python, the script would be interpreted as a python script, but if the first line is #!/path/to/javascript/interpreter, the the script would be interpreted as javascript.
This is the default behavior of the terminal (or just executing a file in general) all you have to do is make the script executable with
chmod u+x test.txt
Then (assuming text.txt is in your current directory) every time you type
./text.txt
It will look at the sh-bang line and use the program there to run text.txt.
If you really want to duplicate built-in functionality, try this.
#!/bin/sh
x=$1
shift
p=$(sed -n 's/^#!//p;q' "$x" | grep .) && exec $p "$#"
exec "$x" "$#"
echo "$0: $x: No can do" >&2
Maybe call it start to remind you of the similarly useful Windows command.
I am hoping someone can help me figure out what setting I might need to overwrite. I am working on a Unix terminal server, running a Linux Xterm linux shell. Everytime I use a command like grep "blah" 2> /dev/null at the shell prompt, the command is run as grep "blah" 2 > /dev/null and needless to say the redirection fails.
xterm version is X.Org 6.8.99.903(238)
I can not update or install anything, this is a locked down production server.
Thanks for any help and illumination on the topic, it is making my grep useless at high directory levels with recursion.
That's Bourne shell syntax, and it doesn't work in c-shell.
The best you can do is
( command >stdout_file ) >&stderr_file
Where you get stdout to one file, and stderr to another. Redirecting just stderr is not possible.
In a comment, you say "A minor note, this is csh". That's not a minor note, that's the cause of the problem. xterm is just a terminal emulator, not a shell; all it does is set up a window that provides textual input and output. csh (or bash, or ...) is the shell, the program that interprets the commands you type.
csh has different syntax for redirection, and doesn't let you redirect just stderr. command > file redirects stdout; command >& file redirects both stdout and stderr.
You say the system doesn't have bash, but it does have ksh. I suggest just using ksh; it will be a lot more familiar to you. Both bash and ksh are derived from the old Bourne shell.
All (?) Unix-like systems will have a Bourne-like shell installed as /bin/sh. Even if you're using csh (or tcsh?) as your interactive shell, you can still invoke sh, even in a one-liner. For example:
sh -c 'command 2>/dev/null'
will invoke sh, which in turn will invoke command and redirect just its stderr to /dev/null.
The purpose of an interactive shell is (mostly) to let you use other commands that are available on the system. sh, or any shell, can be used as just another command.
I'm quite new to cron and crontab.
I've edited the crontab file and I need to execute manually one of commands so I can try it and test it beforehand. How do I do that? If it fails, is there a mode that shows the errors?
Write a shell script that you can test.
Execute that shell script from the crontab.
Remember that cron provides barely any environment - so your script may have to fix that. In particular, your profile will not be used.
Do not get fancy with what you put in the crontab.
Build a debug mode into your shell script.
No, there isn't specifically a mode that shows errors. Usually, if the cron job witters, the output is emailed to you. That is, it sends standard output and standard error information to you if the executed command writes anything to either standard output or standard error.
On MacOS X (10.6.7), the environment I got was (via a crontab entry like 12 37 17 5 * env >/tmp/cron.env):
SHELL=/bin/sh
USER=jleffler
PATH=/usr/bin:/bin
PWD=/Users/jleffler
SHLVL=1
HOME=/Users/jleffler
LOGNAME=jleffler
_=/usr/bin/env
Of those, PWD, _ and SHLVL are handled by the shell. So, to test your script reliably in a cron-like environment, use:
(cd $HOME
env -i \
SHELL=/bin/sh \
USER=$USER \
PATH=/usr/bin:/bin \
HOME=$HOME \
LOGNAME=$LOGNAME \
/path/to/script/you/execute ...
)
The -i option to env means 'ignore all inherited enviroment'; the script will see exactly the five values specified plus anything the shell specifies automatically. With no arguments, env reports on the environment; with arguments, it adjusts the environment and executes a command.
To execute a script "manually" you first have to make it executable by doing:
$ chmod +x yourScriptName
Then do either
$ ./yourScriptName
if you execute it from its path or
$ /full/path/to/yourScriptName
from anywhere.
I have two unix machines, both running AIX 5.3
My $HOME is mounted on machine1.
Using NFS, login machine2 will go to the same $HOME
I login machine2 first, then machine1.
Both using telnet.
The 2 sessions will share the same .sh_history file.
I found out that the fc -l behavior very strange.
In machine2, I issue the commands in telnet:
fc -l
ksh fc -l
Both give the same output.
In machine1,
fc -l
ksh fc -l
give DIFFERENT results
The result for ksh fc -l
is the same as /usr/bin/fc -l
Also, when I run a script like this:
#!/usr/bin/ksh
fc -l
The result is same as /usr/bin/fc -l
Could anyone tell me what happened?
Alvin SIU
Ah, wisdom of the ancients... (Since this post is over a year old.)
Anyway, I just encountered this problem in Solaris 10. Issue seems to be this: When you define a function in /etc/profile, or in any file called by /etc/profile, your HISTFILE variable gets ignored by the Korn shell, and the shell instead uses ".sh_history" when accessing its history. Not sure why this is.
Result is that you see other root shell's commands. You can test it with :
lsof -p $$
or
cat /proc/$$/fd/63
It's possible that the login shell is not ksh or that $HISTFILE is being reset. One thing you can do is echo $HISTFILE in the various situations and see if it's different. Another thing to check is to see what shell you're in using ps.
Bash (default $HOME/.bash_history), for example, will have a different $HISTFILE than ksh (default $HOME/.sh_history).
Another possible reason for the difference is that the builtin fc may be able to see in-memory history that hasn't been written to disk yet (which the external /usr/bin/fc wouldn't be able to see). If this is true, it may be version dependent. Bash, for example, doesn't write history to the file until the shell exits. Ksh (at least the version I'm using) writes it immediately.
I have a script that looks like this
#!/bin/bash
function something() {
echo "hello world!!"
}
something | tee logfile
I have set the execute permission on this file and when I try running the file like this
$./script.sh
it runs perfectly fine, but when I run it on the command line like this
$sh script.sh
It throws up an error. Why does this happen and what are the ways in which I can fix this.
Running it as ./script.sh will make the kernel read the first line (the shebang), and then invoke bash to interpret the script. Running it as sh script.sh uses whatever shell your system defaults sh to (on Ubuntu this is Dash, which is sh-compatible, but doesn't support some of the extra features of Bash).
You can fix it by invoking it as bash script.sh, or if it's your machine you can change /bin/sh to be bash and not whatever it is currently (usually just by symlinking it - rm /bin/sh && ln -s /bin/bash /bin/sh). Or you can just use ./script.sh instead if that's already working ;)
If your shell is indeed dash and you want to modify the script to be compatible, https://wiki.ubuntu.com/DashAsBinSh has a helpful guide to the differences. In your sample it looks like you'd just have to remove the function keyword.
if your script is at your present working directory and you issue ./script.sh, the kernel will read the shebang (first line) and execute the shell interpreter that is defined. you can also call your script.sh by specifying the path of the interpreter eg
/bin/bash myscript.sh
/bin/sh myscript.sh
/bin/ksh myscript.sh etc
By the way, you can also put your shebang like this (if you don't want to specify full path)
#!/usr/bin/env sh
sh script.sh forces the script to be executed within the sh - shell.
while simply starting it from command line uses the shell-environemnt you're in.
Please post the error message for further answers.
Random though on what the error may be:
path specified in first line /bin/bash is wrong -- maybe bash is not installed?