Pass variable from bash to R with commandArgs - r

Question

I'm having a terrible go trying to pass some variables from the shell to R. I am hesitant to post this because I can't figure out a reasonable way to make this reproducible, since it involves a tool that has to be downloaded, and really it's more of a general methodology issue that I don't think needs to be reproducible, if you can just suspend your disbelief and bear with me for a quick minute.
I have arguments that are defined in a bash script: $P, $G, and $O.
I have some if/then statements and everything is fine until I get to the $O options.
This is the first part of the $O section and it works fine. It grabs data from $P and passes it to the twoBitToFa utility from UCSC's genome project and outputs the data correctly in a .fa file. Beautiful. (Although I think using 'stdout' and '>' is perhaps redundant?)
if [ "$O" = "fasta" ]
then
awk '{print $0" "$1":"$2"-"$3}' "$P" |
twoBitToFa -bed=stdin -udcDir=. "$twobit" stdout > "${P%.bed}".fa
fi
The next section is where I am stuck. If the $O option is "bed", then I want to invoke the Rscript command and pass my stuff over to R. I am able to pass my $P, $G, and $O variables without issue, but now I also need to pass the output from the twoBitToFa function. I could add a step and make the .fa file and then pick that up in R, but I am trying to skip the .fa file creation step and output a different file type instead (.bed). Here are some things I have tried:
# try saving twoBitToFa output to variable and including it in the variables passed to R:
if [ "$O" = "bed" ]
then
awk '{print $0" "$1":"$2"-"$3}' "$P" |
myvar=$(twoBitToFa -bed=stdin -udcDir=. "$twobit" stdout) \
Rscript \
GetSeq_R.r \
$P \
$G \
$O \
$myvar
fi
To check what variables come through, my GetSeq_R.r script starts with:
args = commandArgs(trailingOnly=TRUE)
print(args)
and with the above code, the output only includes my $P, $G, and $O variables. $myvar doesn't make it. $P is the TAD-1 file, $G is "hg38", and $O is "bed".
[1] "TAD-1_template.bed" "hg38" "bed"
I am not sure if the way I am trying to pass the data in the variable is wrong. From everything I've read, it seems like it should work. I've also tried using tee to see what is in my stdout at that step like so:
if [ "$O" = "bed" ]
then
awk '{print $0" "$1":"$2"-"$3}' "$P" |
twoBitToFa -bed=stdin -udcDir=. "$twobit" stdout | tee \
Rscript \
GetSeq_R.r \
$P \
$G \
$O
fi
And the data I want to pass to R is correctly shown in my console by using tee. I've tried saving stdout and tee to a variable and passing that variable to R, thinking maybe it's something about twoBitToFa that refuses to be put inside a variable, but was unsuccessful. I've spent hours looking up info about tee, stdout, and passing variables from bash to R. I feel like I'm missing something fundamental, or trying to do something impossible, and would really appreciate some other eyes on this.
Here's the whole bash script, in case that's illuminating. Do I need to define a variable in "$#" for what I am trying to pass to R, even though it's not something I want the user to be aware of? Am I capturing the variable with $myvar incorrectly? Can I get the contents of stdout or tee to show up in R?
Thanks in advance.
for arg in "$#"; do
shift
case "$arg" in
"--path") set -- "$#" "-P" ;;
"--genome") set -- "$#" "-G" ;;
"--output") set -- "$#" "-O" ;;
"--help") set -- "$#" "-h" ;;
*) set -- "$#" "$arg"
esac
done
while getopts ":P:G:O:h" OPT
do
case $OPT in
P) P=$OPTARG;;
G) G=$OPTARG;;
O) O=$OPTARG;;
h) help ;;
\?)
echo "Invalid option: -$OPTARG" >&2
usage
exit 1
;;
:)
echo "Option -$OPTARG requires an argument." >&2
usage
exit 1
;;
esac
done
num_col=$(cat "$P" | awk "{print NF; exit}")
if [ "$num_col" = 3 ]
then
echo -e "\n\n3 column bed file detected; no directional considerations for sequences \n\n"
if [ "$G" = "hg38" ]
then
twobit="https://hgdownload.cse.ucsc.edu/goldenpath/hg38/bigZips/hg38.2bit"
fi
if [ "$G" = "hg19" ]
then
twobit="https://hgdownload.cse.ucsc.edu/goldenpath/hg19/bigZips/hg19.2bit"
fi
if [ "$O" = "fasta" ]
then
awk '{print $0" "$1":"$2"-"$3}' "$P" |
twoBitToFa -bed=stdin -udcDir=. "$twobit" stdout > "${P%.bed}".fa
fi
if [ "$O" = "bed" ]
then
awk '{print $0" "$1":"$2"-"$3}' "$P" |
#myvar=$(twoBitToFa -bed=stdin -udcDir=. "$twobit" stdout) \
Rscript \
GetSeq_R.r \
$P \
$G \
$O \
$myvar
fi
fi