pass a whole string as argument between python and bash

Question

cat /tmp/testme
#!/usr/bin/env  python3
import sys
print(sys.argv[0])
print(sys.argv[1])

It is simple ,just to print argument passed from bash to python.

x="i am a book"
/tmp/testme "i am a book"
/tmp/testme
i am a book

The string i am a book can passed into python program as a whole string.

/tmp/testme  ${x}
/tmp/testme
i
echo ${x}
i am a book

Why python can't deal with ${x} i am a book as a whole,it get only the first character in the string as argument.

Your question is very unclear. Could you please elaborate a little and tell us your goal and what the code is supposed to do? — Arnav Poddar
– Arnav Poddar, Commented Jun 1, 2019 at 1:25
Without double-quotes around it, the shell will try to split the variable's value into words and also expand anything that looks like a wildcard into a list of matching filenames. You generally don't want either of these (and if you do, you probably want it in a different form), so you should almost always put double-quotes around variable references. — Gordon Davisson
– Gordon Davisson, Commented Jun 1, 2019 at 1:49

Shane Bishop · Accepted Answer · 2019-06-01 13:47:12Z

1

When you execute the line /tmp/testme ${x}, bash will expand the contents of x, and will ultimately execute /tmp/testme i am a book. Therefore, sys.argv will become ['/tmp/testme', 'i', 'am', 'a', 'book'].

To achieve the desired behaviour, ${x} should be quoted, like "${x}". Then bash will execute /tmp/testme 'i am a book'.

Here is an example with a bash script. With set -x, bash will print commands and their arguments as they are executed, after all variables have been evaluated.

$ cat testme
#!/usr/bin/env python3
import sys
print(sys.argv)

$ cat exampleBashScript.sh 
#!/usr/bin/env bash
set -x

x="i am a book"
./testme ${x}
./testme "${x}"

$ ./exampleBashScript.sh 
+ x='i am a book'
+ ./testme i am a book
['./testme', 'i', 'am', 'a', 'book']
+ ./testme 'i am a book'
['./testme', 'i am a book']

edited Jun 1, 2019 at 13:47

answered Jun 1, 2019 at 13:30

Shane Bishop

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