python 2 subprocess check_output不返回错误输出

Question

I have this method

def do_sh_shell_command(string_command, env_variables=None):
    cmd = shlex.split(string_command)
    try:
       p = subprocess.check_output(string_command, shell=True,
                                   env=env_variables) # shell=True means sh shell used 
    except subprocess.CalledProcessError as e:
        print 'Error running command: ' + '"' + e.cmd + '"' + ' see above shell error'
        print 'Return code: ' + str(e.returncode)
        return e.returncode, e.cmd
    return 0, p

which work but for some reason doesn't return the error output from a specfici command

def hold_ajf_job(job_order_id):
    #print 'ctmpsm -UPDATEAJF ' + job_order_id + ' HOLD'
    return do_sh_shell_command('ctmpsm -UPDATEAJF ' + job_order_id + ' HOLD')

hold_ajf_job('0e4ba')
do_sh_shell_command('lsl')

output:

ctmpsm -UPDATEAJF 0e4ba HOLD
Error running command: "ctmpsm -UPDATEAJF 0e4ba HOLD" see above shell error
Return code: 1
/bin/sh: lsl:  not found
Error running command: "lsl" see above shell error
Return code: 127

when I run command ctmpsm -UPDATEAJF 0e4ba HOLD just form the normal shell i get the below error output

ctmtest1-tctmsv80 [288] ctmpsm -UPDATEAJF 0e4ba HOLD
Failed to Hold Orderno 0000e4ba. (rc=JOBSTATINCM).

This is different to the un-useful error output in my python code and I can't for the life of me figure out why?

UPDATE:

Trying stderr=subprocess.STDOUT

def do_sh_shell_command(string_command, env_variables=None):
    cmd = shlex.split(string_command)
    try:
       p = subprocess.check_output(string_command, stderr=subprocess.STDOUT, shell=True,
                                   env=env_variables) # shell=True means sh shell used 
    except subprocess.CalledProcessError as e:
        print 'Error running command: ' + '"' + e.cmd + '"' + ' see above shell error'
        print 'Return code: ' + str(e.returncode)
        return e.returncode, e.cmd
    return 0, p

output:

Error running command: "ctmpsm -UPDATEAJF 0e4ba HOLD" see above shell error
Return code: 1
Error running command: "lsl" see above shell error
Return code: 127

Now errors have completely disappeared?

Answer 1

As documented , when check_output raises an exception, it places the output of the command in the output attribute of the exception object. You can do the following:

try:
    p = subprocess.check_output(string_command, stderr=subprocess.STDOUT,
                                shell=True, env=env_variables)
except subprocess.CalledProcessError as e:
    print e.output
    print 'Error running command: ' + '"' + e.cmd + '"' + ' see above shell error'
    print 'Return code: ' + str(e.returncode)
    return e.returncode, e.cmd
return 0, p

Answer 2

By specifying stderr=subprocess.STDOUT , you can make the output written to standard error to be redirected to standard output.

p = subprocess.check_output(
    string_command,
    shell=True,
    stderr=subprocess.STDOUT,
    env=env_variables)