Puppy Linux Discussion Forum

qpdf has some options which test various things about a pdf file and output a return code for easy scripting.
The manual for qpdf suggests that I can use code like this:

if [ qpdf --is-encrypted *3* ]; then echo "yes"; else echo "no"; fi

It does not work (see second to last command below). Is the syntax in the manual wrong, or is there something weird about my bash or something in my environment?

#  qpdf --is-encrypted *2*
#  echo $?
2
#  qpdf --is-encrypted *3*
#  echo $?
0
#  qpdf --is-encrypted *2*
#  if [ $? = 0 ]; then echo "yes"; else echo "no"; fi
no
#  qpdf --is-encrypted *3*
#  if [ $? = 0 ]; then echo "yes"; else echo "no"; fi
yes
#  if [ qpdf --is-encrypted *3* ]; then echo "yes"; else echo "no"; fi
-bash: [: --is-encrypted: binary operator expected
no
#  if [ $(qpdf --is-encrypted *3*) ]; then echo "yes"; else echo "no"; fi
no

Thanks.

@disciple - I think *3* within square backets alone needs to be inside single quotes.

Perhaps I'm not following what you mean - neither of these syntaxes work:

#   if [ qpdf --is-encrypted '*3*' ]; then echo "yes"; else echo "no"; fi
-bash: [: --is-encrypted: binary operator expected
no
#  if [ 'qpdf --is-encrypted *3*' ]; then echo "yes"; else echo "no"; fi
yes
#  if [ 'qpdf --is-encrypted *2*' ]; then echo "yes"; else echo "no"; fi
yes

disciple wrote: ↑Tue Dec 13, 2022 7:24 am

Is the syntax in the manual wrong, or is there something weird about my bash or something in my environment?

The syntax in the manual is wrong.

qpdf manual wrote:

Use with the --password option to specify the password to test.

The choice of exit status 0 to mean that a password is required is to enable code like

Code: Select all

if [ qpdf --requires-password file.pdf ]; then
    # prompt for password
fi

[↑]

qpdf here is not a command but a first positional parameter to [ a.k.a. test:

root# if [ whoami ]; then echo "yes"; fi # whoami command doesn't run
yes
root# if whoami ; then echo "yes"; fi # whoami command runs
root
yes

It should be (without [...]):

if qpdf --requires-password file.pdf ; then
    # prompt for password
fi

Use if [ $? -eq 2 ]; then if you need to test for a specific return value.

Burunduk wrote: ↑Tue Dec 13, 2022 8:43 am

disciple wrote: ↑Tue Dec 13, 2022 7:24 am

Is the syntax in the manual wrong, or is there something weird about my bash or something in my environment?

The syntax in the manual is wrong.

Great, thanks.
Of course, for the potential benefit of others, if I only want to confirm that the exit code is zero, or only want to confirm that the exit code is not zero, it is probably more normal just to use && or ||

#  qpdf --is-encrypted *x*2* && echo "test"
#  qpdf --is-encrypted *x*2* || echo "test"
test
#  qpdf --is-encrypted *x*3* && echo "test"
test
#  qpdf --is-encrypted *x*3* || echo "test"
#