For example,
I executed "pwd" and it shows the current working directory. Then if I want to reuse that result in my another command, it would convenient to get it via a Unix command or built-in variable. Does it exist?
You can get the result, as in return code, using $?. In order to get the output you'll need to explicitly keep it around - e.g. with:
MYVAR=`pwd`
echo $MYVAR
Use $? inorder to get the status of the last executed command. Its value will be zero if the last executed command was successful else non zero.
The internal variable $? holds the return value of the last executed command or program. Example: http://tldp.org/LDP/abs/html/complexfunct.html#MAX.
If you don't need to run one command first, you can also try using pipes | to connect commands. I am constantly piping long directory listings over to more, so I can page through the results, with
ls -al | more
so if you want to use the results of running pwd as input to another program, you can try something like piping the results of pwd over to more with
pwd|more
Related
I need to check the exit status of a piped command from R on Debian, like here, but cannot make run echo "${pipestatus[1]}" successfully from R using system2/system function. The command works properly when I use command line.
The command I am trying to use in R can look like this (the shell I use is zsh):
system2("false", args = "|true;echo '${pipestatus[1]}'")
After some testing I can see that the exit status checking command cannot be quoted properly but I cannot figure out the correct way to do so.
Am I right that quoting this command properly is the issue? How to run this (echo "${pipestatus[1]}") command from R? Are there any alternatives to using the command in question to check exit status?
You can’t use zsh features here, since system2 doesn’t invoke a shell.
Instead, you’ll either need to use a raw system call or, better, explicitly invoke the shell in system2. You’ll also need to use double quotes instead of single quotes around ${pipestatus[1]} to allow expansion — otherwise zsh will interpret it as a literal string.
system2('zsh', c('-c', shQuote('false|true; echo "${pipestatus[1]}"')))
I need to get different SFTP exit codes for each error. For instance 'no such file or directory' --> exit code=552 or 550 instead of returning 1.
I've tried the following and it did not work:
//A05FTP EXEC PROC=SFTPROC,COND=(0,NE)
//COPSFTP.MYSTDIN DD *
host="xpto.xpty.xptz"
lzopts mode=text
cd /home/apl/files/unl
ls
a=`ls | wc -l`
echo `$a`
echo $?
QUIT
//*
and the output in spool is:
cozsftp> lzopts mode=text
mode=text
cozsftp> lzopts mode=text
mode=text
cozsftp> cd /home/apl/files/unl
Ý09.807¨ Invalid command.
cozsftp> a= 1
CoZBatchÝI¨: returning rc=exitcode=1
Can anyone help me?
COZBATCH allows you to embed shell scripts into JCL, so you don't need to use BPXBATCH. BPXBATCH really is a poor utility. If you're using Co:Z then good for you it rocks.
If you want to run shell commands you need to use the ! escape character.
!echo $a
FWIW, SFTP always returns 1 on error. I'm not sure if you can change that. Errors should be logged in the sysout.
Your problem may simply be the echo `$a`. Try enclosing with quotes instead of tick marks.
More generally, if you want to do more detailed error checking, instead of using the SFTP procedure (SFTPROC), I think you'd do better to write yourself a simple script that you execute with BPXBATCH. The script would issue the same SFTP commands, but you could capture and redirect the output (STDOUT/STDERR) and based on the return value ($?) and any error messages, you could certainly detect all the unusual conditions you might want.
What is the right way to assign commands into variable . a.k.a how should i use quote commas and how assign it to variable , so the command is up to date? For example
i am at home/desktop
i assign variable
b=`pwd`
echo "$b" // home/desktop
but when i change the directory
cd games
pwd // home/desktop/games
echo "$b" // home/desktop
it does not update. Also i want to do something like
g="-l"
ls $g
is it possible?
Variables never update automatically, you have to re-assign them, i.e.,
b=`pwd`
echo "$b" // home/desktop
cd games
pwd // home/desktop/games
b=`pwd`
echo "$b" // home/desktop/games
as for your second question, I think that's only possible using eval:
g=" -la"
eval "ls"$g
BE VERY CAREFUL WITH THIS It's very easy to write something that can compromise security and indeed most people (including myself!) would strongly advise you never to use eval unless all else has failed.
Consider the code above for demonstration purposes only, under no circumstances to be used in a production system.
I think you are confusing assigning variables with aliases.
assigning a variable means you store the result of the command in a variable
what this command does
b=`pwd`
is running pwd and stores the answer in a variable b.
and alias means giving some command a different name. so running alias b pwd will make it so whenever you run b, you will actually run pwd
b is only set when you run the first command (assigning the output of pwd to b, it doesn't link those items together (so that b gets set on every invocation). There are ways to do that also (do man bash on your machine) (for example, the shell variable $PWD contains this information.
to your second question, yes, you can do that, but a nice way to so it is to use alias. So, alias ll='ls -l' creates a command on your system that will run ls -l when you type ll
I'm writing a program (in python) that calls a separate program (via subprocess). I'm finding that in some cases the sub program is getting stuck running. I can see the sub-program by running top, and if i press "c", I can see the full command line.
What I want, is to be able to stick debugging data (like current thread id, etc) in the command line when i'm calling the sub program, so I can futher debug my problem.
Is there a way to put comments in command line arguments such that they show up in top?
I can't think of a direct way but you could write a little shell script to which you pass the actual command to run plus argument and debugging information. It would show up in the top/ps output.
Instead of making them comments, put them in the environment. For example, if you have a /proc file system, you could do:
FOO=value cmd
When top shows the pid of the command, do:
tr '\000' '\012' < /proc/pid/environ | grep FOO
to see the value of FOO in the environment of the cmd. If the values contain newlines, you will need to be more careful about the display, something like:
perl -n0E 'say if /FOO/' /proc/pid/environ
All,
I want to execute a unix statement in expect script.The unix statement outputs rsize value for a process. I haven't programmed in expect before.
This is my code:
#!/usr/bin/expect
set some_host "some host"
set Mycmd "top -l 1 -stats pid,rsize,command | grep Process_Name| awk '{print \$2};'"
spawn telnet localhost $some_host
expect "login:"
send "myDevice\r"
expect "Password:"
send "$password\r"
expect "\$"
send "$Mycmd\r"
When I execute this, I don't get any output. What's the correct syntax to execute the unix statement? How do I get this to work so that I get the correct rsize value as the output?
Always a good idea to try to escape with ascii, try \0442 for \$2 or try something like \\$2
.Also you can debug the script to find why you have no output if you insert 'exp_internal 1' without quotes at the second line.
Is it possible to get the output without having to add the "interact" statement
Yes, it is. Other statements which wait for the output will also do; you could add e. g.
expect -re "\n\[0-9]+"
to the end of your script.