Bad Substitution error with pdfgrep as variable? - bash

Question

I'm using a bash script to parse information from a PDF and use it to rename the file (with the help of pdfgrep). However, after some working, I'm receiving a "Bad Substitution" error with line 5. Any ideas on how to reformat it?
shopt -s nullglob nocaseglob
for f in *.pdf; do
id1=$(pdfgrep -i "ID #: " "$f" | grep -oE "[M][0-9][0-9]+")
id2=$(pdfgrep -i "Second ID: " "$f" | grep -oE "[V][0-9][0-9]+")
$({ read dobmonth; read dobday; read dobyear; } < (pdfgrep -i "Date Of Birth: " "$f" | grep -oE "[0-9]+"))
# Check id1 is found, else do nothing
if [ ${#id1} ]; then
mv "$f" "${id1}_${id2}_${printf '%02d-%02d-%04d\n' "$dobmonth" "$dobday" "$dobyear"}.pdf"
fi
done

Answer 1

There are several unrelated bugs in this code; a corrected version might look like the following:
#!/usr/bin/env bash
shopt -s nullglob nocaseglob
for f in *.pdf; do
id1=$(pdfgrep -i "ID #: " "$f" | grep -oE "[M][0-9][0-9]+") || continue
id2=$(pdfgrep -i "Second ID: " "$f" | grep -oE "[V][0-9][0-9]+") || continue
{ read dobmonth; read dobday; read dobyear; } < <(pdfgrep -i "Date Of Birth: " "$f" | grep -oE "[0-9]+")
printf -v date '%02d-%02d-%04d' "$dobmonth" "$dobday" "$dobyear"
mv -- "$f" "${id1}_${id2}_${date}.pdf"
done
< (...) isn't meaningful bash syntax. If you want to redirect from a process substitution, you should use the redirection syntax < and the process substitution <(...) separately.
$(...) generates a subshell -- a separate process with its own memory, such that variables assigned in that subprocess aren't exposed to the larger shell as a whole. Consequently, if you want the contents you set with read to be visible, you can't have them be in a subshell.
${printf ...} isn't meaningful syntax. Perhaps you wanted a command substitution? That would be $(printf ...), not ${printf ...}. However, it's more efficient to use printf -v varname 'fmt' ..., which avoids the overhead of forking off a subshell altogether.
Because we put the || continues on the id1=$(... | grep ...) command, we no longer need to test whether id1 is nonempty: The continue will trigger and cause the shell to continue to the next file should the grep fail.

Answer 2

Do what Charles suggests wrt creating the new file name but you might consider a different approach to parsing the PDF file to reduce how many pdfregs and pipes and greps you're doing on each file. I don't have pdfgrep on my system, nor do I know what your input file looks like but if we use this input file:
$ cat file
foo
ID #: M13
foo
Date Of Birth: 05 21 1996
foo
Second ID: V27
foo
and grep -E in place of pdfgrep then here's how I'd get the info from the input file by just reading it once with pdfgrep and parsing that output with awk instead of reading it multiple times with pdfgrep and using multiple pipes and greps to extract the info you need:
$ grep -E -i '(ID #|Second ID|Date Of Birth): ' file |
awk -F': +' '{f[$1]=$2} END{print f["ID #"], f["Second ID"], f["Date Of Birth"]}'
M13 V27 05 21 1996
Given that you can use the same read approach to save the output in variables (or an array). You obviously may need to massage the awk command depending on what your pdfgrep output actually looks like.