Pass Variable to Python in Bash Script

Question

I'm trying to transfer a variable in a bash-script to an embedded python-function. A minimal example of the script I'm using is given below:

#!/bin/bash

function python_print() {
PYTHON_ARG="$1" python - <<END
import os
p = str(os.environ['PYTHON_ARG'])
print('The Variable is ' + p)
END
}

DIRIN=$1
FULLPATH=$ realpath $OUTFILE
python_print $FULLPATH

Running the script gives me: "The variable is "; so it seems the argument FULLPATH is not transfered to the function. The strange thing is, the code works if "$FULLPATH" is replaced either with "$1", "$DIRIN" or any hardcoded string. Where is my mistake? I'm grateful for any advice!

Nahuel Fouilleul · Accepted Answer · 2018-01-22 15:51:43Z

1

The problem is not in python_print function (note that function keyword is redundant with ()). but in FULLPATH assignment and function call

correct syntax

FULLPATH=$(realpath "$OUTFILE")
python_print "$FULLPATH"

no space between = and value in assignment
double quotes around variable expansion in function call
expansion must be double quoted except
- if $ appears just after = in assignment
- conditions between double brackets [[ ]]

note that

FULLPATH=$ realpath $OUTFILE

is not affecting FULLPATH in current shell process environment, it just sets FULLPATH to $ to realpath execution process environment also output is not captured.

edited Jan 22, 2018 at 15:51

answered Jan 22, 2018 at 15:23

Nahuel Fouilleul

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liberforce · Accepted Answer · 2018-01-22 15:04:08Z

0

Just either:

export your bash variable so it is available in os.environ
or use positional parameters and read it from sys.argv

answered Jan 22, 2018 at 15:04

liberforce

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Pass Variable to Python in Bash Script

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