OSError Errno 8 Exec format error

Question

I am having hard time parsing the arguments to subprocess Popen   I am trying to execute a script on my Unix server  The script syntax when running on shell prompt is as follows   usr local bin script hostname    lt hostname gt  -p LONGLIST  No matter how I try  the script is not running inside subprocess Popen  The space before and after     is mandatory   import subprocess Out   subprocess Popen    usr local bin script    hostname       actual server name    -p    LONGLIST   shell True stdout subprocess PIPE stderr subprocess PIPE    The above does not work   And when I use shell False  I get OSError   Errno 8  Exec format error

User · Answer

Have you tried this   Out   subprocess Popen   usr local bin script hostname   actual server name -p LONGLIST  split    shell False stdout subprocess PIPE stderr subprocess PIPE     Edited per the apt comment from  J F Sebastian

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OSError   Errno 8  Exec format error can happen if there is no shebang line at the top of the shell script and you are trying to execute the script directly  Here s an example that reproduces the issue    gt  gt  gt  with open  a   w   as f  f write  exit 0     create the script       gt  gt  gt  import os  gt  gt  gt  os chmod  a   0b111101101    rwxr-xr-x make it executable                         gt  gt  gt  os execl    a      a         execute it                                             Traceback  most recent call last     File   lt stdin gt    line 1  in  lt module gt    File   usr lib python2 7 os py   line 312  in execl     execv file  args  OSError   Errno 8  Exec format error   To fix it  just add the shebang e g   if it is a shell script  prepend    bin sh at the top of your script    gt  gt  gt  with open  a   w   as f  f write     bin sh nexit 0         gt  gt  gt  os execl    a      a     It executes exit 0 without any errors     On POSIX systems  shell parses the command line i e   your script won t see spaces around   e g   if script is      usr bin env python import sys print sys argv    then running it in the shell      usr local bin script hostname     lt hostname gt   -p LONGLIST   produces      usr local bin script    hostname          lt hostname gt     -p    LONGLIST     Note  no spaces around      I ve added quotes around  lt hostname gt  to escape the redirection metacharacters  lt  gt    To emulate the shell command in Python  run   from subprocess import check call  cmd      usr local bin script    hostname          lt hostname gt     -p    LONGLIST   check call cmd    Note  no shell True  And you don t need to escape  lt  gt  because no shell is run    Exec format error  might indicate that your script has invalid format  run     file  usr local bin script   to find out what it is  Compare the architecture with the output of     uname -m

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I will hijack this thread to point out that this error may also happen when target of Popen is not executable  Learnt it hard way when by accident I have had override a perfectly executable binary file with zip file

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If you think the space before and after     is mandatory  try it as separate item in the list   Out   subprocess Popen    usr local bin script    hostname         actual server name    -p    LONGLIST   shell True stdout subprocess PIPE stderr subprocess PIPE

User · Answer

It wouldn t be wrong to mention that Pexpect does throw a similar error   python -c  import pexpect  p pexpect spawn   usr local ssl bin openssl 1 1 0f  version    p interact    Traceback  most recent call last     File   lt string gt    line 1  in  lt module gt    File   usr lib python2 7 site-packages pexpect py   line 430  in   init       self  spawn  command  args    File   usr lib python2 7 site-packages pexpect py   line 560  in  spawn     os execv self command  self args  OSError   Errno 8  Exec format error   Over here  the openssl 1 1 0f file at the specified path has exec command specified in it and is running the actual openssl binary when called   Usually  I wouldn t mention this unless I have the root cause  but this problem was not there earlier  Unable to find the similar problem  the closest explanation to make it work is the same as the one provided by  jfs above   what worked for me is both   adding   bin bash at the beginning of the command or file you are facing the problem with  or adding shebang    bin sh as the first line    for ex    python -c  import pexpect  p pexpect spawn   bin bash  usr local ssl bin openssl 1 1 0f  version    p interact    OpenSSL 1 1 0f  25 May 2017

[python] OSError: [Errno 8] Exec format error

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