How to redirect command output using os.execvp() in python

Question

I am invoking shell script using os.execvp() in python. my shell script has some echo statements whcih I want to redirect in file.

Here is what I am trying:

cmd = "/opt/rpm/rpm_upgrade.sh >& /opt/rpm/upgrader.log"
cmdline = ["/bin/sh", cmd]
os.execvp(cmdline[0], cmdline)

Below is the error I am getting:

Error:   /bin/sh: /opt/rpm/rpm_upgrade.sh >& /opt/rpm/upgrader.log: No such file or directory

Can any one help?

No such file or directory - I wonder what could that possibly mean?... — Maxim Egorushkin
– Maxim Egorushkin, Commented Apr 27, 2016 at 10:22
@alpert: Yes. The rpm_upgrade.sh file is exist. That means /opt/rpm/ directory is also exist. — Amar Patil
– Amar Patil, Commented Apr 27, 2016 at 10:35

John Zwinck · Accepted Answer · 2016-04-27 10:54:42Z

1

This is happening because you are passing this entire string as if it were the program name to execute:

"/opt/rpm/rpm_upgrade.sh >& /opt/rpm/upgrader.log"

The easy way to fix this is:

cmdline = ["/bin/sh", "/opt/rpm/rpm_upgrade.sh",
           ">&", "/opt/rpm/upgrader.log"]
os.execvp(cmdline[0], cmdline)

Now sh will receive three arguments rather than one.

Or you can switch to the more full-featured subprocess module, which lets you redirect output in Python:

import subprocess
with open("/opt/rpm/upgrader.log", "wb") as outfile:
    subprocess.check_call(["/opt/rpm/rpm_upgrade.sh"], shell=True,
                          stdout=outfile, stderr=subprocess.STDOUT)

edited Apr 27, 2016 at 10:54

answered Apr 27, 2016 at 10:37

John Zwinck

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3 Comments

Amar Patil Over a year ago

It is fixing above error but problem is This fix is not redirecting my rpm_upgrade.sh 's echo statements to /opt/rpm/upgrader.log file. It is still printing on console.

John Zwinck Over a year ago

@AmarPatil: I've added perhaps a better code snippet to try to solve that problem.

Amar Patil Over a year ago

When I use code "process = Popen("rpm -Uvh /opt/rpm/new/client-4.1-5470.x86_64.rpm", stdout=PIPE, shell=True) process.communicate() " Its hangs for long time. Anyone help me here ?

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