Why do we exit issuing an echo command while executing a program?
As far as I know, the echo command for console windows is:
$ echo $
And for windows is:
$ echo %ERRORLEVEL%
When the child process ends, the set variable ERRORLEVEL contains an integer returned by it. ERRORLEVEL is measured 0 if the process was successful (i.e. return 0). OTOH, 1 or greater if the process encountered an error.
However, I don't know what do you exactly mean by:
echo command after executing a program
I never ran this command neither I've seen anywhere.
Related
This is the Clang version of:
Make gdb quit automatically on successful termination?
How to have gdb exit if program succeeds, break if program crashes?
Running my application many times, programmatically, over a large number of possible inputs, I've occasionally encountered a segmentation fault.
I'd like each test invocation to be run under lldb so that I can get a backtrace for further debugging. If an invocation exits without a crash, I'd like lldb to automatically quit so that the test harness progresses to the next iteration. This way I can set the whole thing off over lunchtime and only have the suite interrupted when something crashes.
Bonus points for having lldb auto-quit in all cases, but first print a backtrace if the program crashed.
I'm currently able to automate at least the initial run command:
lldb -o run -f $CMD -- $ARGS
I'm having difficulty finding an online command reference but it looks like the -batch command line option will get you the basic "exit on success/prompt on fail" behaviour.
For a backtrace and auto-quit on failure I think you need the --source-on-crash option...
-K <filename>
--source-on-crash <filename>
When in batch mode, tells the debugger to source this file of lldb
commands if the target crashes.
So, create the command file with something like...
echo -e 'bt\nquit' > lldb.batch
and then invoke as...
lldb --batch -K lldb.batch -o run -f $CMD -- $ARGS
I am running this very simple c++ code:
int main()
{
return -1;
}
But when I compile it with g++ and run it (on ubuntu 14.04) it goes through and I get no errors. The book that I am reading, "C++ Primer" says that I should receive an error, so I was wondering if someone could show me what I am doing wrong.
Your program runs normally, then returns a status of -1 to the environment. If you don't look at that status, you're not going to see any indication of an error.
If you're running from the bash shell, you can do something like:
if ./my_program ; then
echo Success
else
echo Failure
fi
or, on one line:
if ./my_program ; then echo Success ; else echo Failure ; fi
or, if you want to be obscure:
./my_program && echo Success || echo Failure
More simply:
./my_program
echo $?
Incidentally, returning a status of -1 is not a portable way to indicate failure. I suggest adding #include <cstdlib> to the top of your program and using return EXIT_FAILURE;. (The value of EXIT_FAILURE is typically 1, but it will be whatever it needs to be to denote failure on the system you're using.)
The code that you've written here is perfectly legal C++. The program runs and then signals an exit code of -1. On some operating systems, if a program terminates with a nonzero exit code, the OS will report an error to the user indicating that something weird happened. On Ubuntu, though, programs that terminate with nonzero exit codes don't trigger an explicit error message, so what you're seeing is the expected behavior.
The return value of main is what's called an exit code. If you run your program from a shell (such as bash on a Unix system or the CMD on Windows), you can examine the exit code. By convention, nonzero exit codes usually imply that something erroneous happened. For instance, your g++ compiler outputs a nonzero exit code if there's a compile error and 0 if everything goes correctly.
Since you said you're on Ubuntu, I assume you're using either bash or dash to run this program. Try running the program and then do echo $? after running the program. You should see the exit code your program returned.
Completely new to bash scripts, trying to make a script to compile and run all cpp files that start with "blah". What I have so far is
#1/bin/bash
for i in blah*.cpp
do
if g++ "$i" -o "${i%.cpp}.out"; then
/Users/[directory]/Desktop/"${i%.cpp}.out" #to run each testcase
else
echo "failed"
fi
done
I need to know how many blah files succeeded in running (I can either make the c++ programs return 1 or just cout "succeeded", any way to tell would be fine), and I'm having trouble figuring out how to get the return status of each program or how to use the output from each program run and see if it says "succeeded".
Have your test case return 1 for success and 0 for failure. The return value can then be used as follows:
counter=0
for i in blah*.cpp
do
if g++ "$i" -o "${i%.cpp}.out"; then
if /Users/[directory]/Desktop/"${i%.cpp}.out" ; then
counter=$((counter+1))
else
echo "failed to run"
fi
else
echo "failed to build"
fi
done
echo "$counter tests succeeded"
I asked this question on the Informatica forums, but no one knew the answer, so now I'm coming here for some help.
To my understanding, anything in a "post-session success command" field should be passed to the appropriate command interface and executed. However, when I use an IF statement, it fails. Any ideas?
"IF 1==1 echo.bob >> f:\filename.txt"
This works when I type it manually into the terminal (DOS in this case). But when I throw it into a reusable command task, I get this:
ERROR
POST-SESS
CMN_1949
Error: [Pre/Post Session Command] Process id 2996. The shell command failed with exit code 1.
PS: Using 9.5.1 Hotfix 1
I think the problem is not in how Informatica executes commands. The problem lies in how DOS return error codes, and specifically that some commands, like IF and ECHO does'nt. (The return code Informatica picks up from DOS can be seen with echo %ERRORLEVEL% in DOS, and I'll use the name DOS here for convenience even though under Windows now this is'nt strictly correct)
Run these commands in succession:
REM "cd" sets ERRORLEVEL => ERRORLEVEL is set to 0
cd c:\
echo %ERRORLEVEL%
REM "echo" does not set ERRORLEVEL => ERRORLEVEL is left unchanged
echo.bob >> c:\filename.txt
echo %ERRORLEVEL%
REM "echo" does not set ERRORLEVEL => ERRORLEVEL is left unchanged
echo.bob >> c:\thisdirdontexist\filename.txt
echo %ERRORLEVEL%
The first CD set a return code, in this case to 0.
The following ECHO (with or without the IF test) does not change the return code, thus it remains 0 even though the last ECHO fails.
If the first CD command would have returned an error;
#echo off
REM "cd" sets ERRORLEVEL => ERRORLEVEL is set to 1
cd xxxxxx
echo %ERRORLEVEL%
then all the subsequent ECHO would return 1 and Informatica would fail them both.
This said it is still strange since each post-session success command in Informatica is executed under its own cmd-shell, so the initial ERRORLEVEL for every command should allways be 0. I can't explain that and unfortunately I can't actually test this in Informatica as we run under UNIX, but I'm pretty sure this is at least part of the problem.
To get around the problem you should make sure that you set the "Fail task if any command fails" option on the property-tab. This makes Informatica use the cmd/c option and since this set a proper return code Informatica should be able to pick up the error (or success) correctly. If this still doesn't work properly try change the command yourself to:
cmd /c "IF 1==1 echo.uncle >> c:\filename.txt"
Here I get a bash file b.sh:
#!/bin/sh
if [ ! -f somefile.txt ]; then
..................
fi
in the bash file ,I try to check whether somefile called "somefile.txt" exist, if not, I would consider it as an error and exit.
And I run this bash file in c++:
::system("sh b.sh")
What should I fill in the "..............." in that bash file and what should I do in c++ code to catch exception when the "somefile.txt" is not found.
Put:
exit 1
in the script -- by convention, any non-zero exit code is considered failure.
In the C++ code, system() returns the termination status of the command. See the documentation of wait() for details of interpreting this, or you can just check if it's non-zero if you want to know if there was any error.