linux - crash shell: any way to check if a command executed Successfully

06
2014-04

limovala

I am automating a test using crash package.

is there some thing like $? in bash shell, which can be used to check if previous command is executed success fully or not.

eg : when command

crash> bt -a

is executed, how to know if it was successfull or not.
only solution in my mind is greping through the result
But its not reliable when the enviornmentchanges.

this is what i get when I try echo $?

crash> bt asd
bt: invalid task or pid value: asd
crash> $?
crash: command not found: $?
crash> echo $?
0
crash>
crash> q
root@at0012-ubuntu:~/crashKernel#

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Related Answers

Studer

You can use the subprocess module under Python 3 or the commands module for Python 2 as follow :

status, result = subprocess.getstatusoutput("ls -al")

status, result = commands.getstatusoutput("ls -al")

Then test the value of status.

Examples from the website :

>>> import subprocess
>>> subprocess.getstatusoutput('ls /bin/ls')
(0, '/bin/ls')
>>> subprocess.getstatusoutput('cat /bin/junk')
(256, 'cat: /bin/junk: No such file or directory')
>>> subprocess.getstatusoutput('/bin/junk')
(256, 'sh: /bin/junk: not found')

djmc

couldn't you use the "which" command somehow? the which command automatically performs a lookup for an application in the paths. I think you would merely need to call this command and pass the name of the command you want to look up, then parse the results.

Gabriel L. Oliveira

I finally left it working this way:

try:

    cmd_grep = ["ack-grep", "--no-color", "--max-count=1", "--no-group", function_definition, file_path]

    first_exec = Popen(cmd_grep,stdout=PIPE)

    execution = Popen(cmd_sed, shell=True, stdin=first_exec.stdout, stdout=PIPE)

except:

    #use grep instead

    cmd_grep = cmd_grep = r'grep -R -n "' + function_definition + '" ' + file_path

    execution = Popen(cmd_grep + '|' + cmd_sed,shell=True,stdout=PIPE)

output = execution.stdout.read()

Jeet

For situations like this, I use:

def find_program(prog_filename, error_on_missing=False):
    bdirs = ['$HOME/Environment/local/bin/',
             '$HOME/bin/',
             '/share/apps/bin/',
             '/usr/local/bin/',
             '/usr/bin/']
    paths_tried = []
    for d in bdirs:
        p = os.path.expandvars(os.path.join(d, prog_filename))
        paths_tried.append(p)
        if os.path.exists(p):
            return p
    if error_on_missing:
        raise Exception("*** ERROR: '%s' not found on:\n  %s\n" % (prog_filename, "\n  ".join(paths_tried)))
    else:
        return None

Then you can do something like:

grep_path = find_program('ack_grep', False)
if grep_path is None:
    # default to standard system grep
    grep_path = 'grep'

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linux - crash shell: any way to check if a command executed Successfully