How to use for loop in Subprocess.run command

Question

I'm using subprocess.run to run a command that has a for loop in it but not getting back the expected result. Here's a simplified case that shows the issue. In bash shell:

for i in {1..3}; do echo ${i}; done

The result is:

1
2
3

Which is what I expect and want. However in my code when I execute this following:

subprocess.run("for i in {1..3}; do echo ${i}; done", shell=True, check=True)

the result printed on my shell is {1..3}

But what I want the result to be is:

1
2
3

like when I execute the code in my shell. Would appreciate any insights on how to fix this, thanks!

billy · Answer 1 · 2023-02-09T21:36:52.523

1

I would recommend using subprocess.popen:

from subprocess import popen
process = subprocess.Popen("bash for i in {1..3}; do echo $i; done")
try:
    outs, errs = process.communicate(timeout=15)
except TimeoutExpired as e:
    process.kill()
    outs, errs = process.communicate()

Or, using your original line of code:

subprocess.run("bash for i in {1..3}; do echo $i; done", shell=True, check=True, capture_output=True)

I was able to gleam this information from the subprocess doc's located here: Subprocess Pypi Docs

Regards, and I hope this helps.

edited Feb 09 '23 at 21:36

answered May 14 '19 at 02:53

billy

27
8

Thanks for the answer! – Justin Owusu May 15 '19 at 14:21
Not a problem at all! – billy May 15 '19 at 23:08
2

I'm getting: No such file or directory: 'bash for i in {1..3}; do echo ${i}; done' – Osama Bin Saleem Mar 14 '22 at 12:56
This gives me `Syntax error: "do" unexpected` – JoshuaF Mar 14 '22 at 18:10
the issue is at the string interpolation, ill update the answer. – billy Feb 09 '23 at 21:36

score 0 · Answer 2 · answered May 14 '19 at 02:46

0

You would want to spawn a subshell:

subprocess.run("sh -c 'for i in {1..3}; do echo ${i}; done'", shell=True, check=True)

answered May 14 '19 at 02:46

l'L'l

44,951
10
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146

Thanks for answering, this still gave me the ```{1..3}``` result again. Did this give you the ```1 2 3``` result? – Justin Owusu May 14 '19 at 14:15

score 0 · Answer 3 · answered May 14 '19 at 03:01

0

In case of python3:

import subprocess
result = subprocess.getoutput("""for i in {1..3}; do echo ${i}; done""")
print(result)

answered May 14 '19 at 03:01

ashish14

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1
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Thanks for answering, this still gives me the ```{1..3}``` result. Did this give you the ```1 2 3``` result? – Justin Owusu May 14 '19 at 14:13

How to use for loop in Subprocess.run command

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