I want a to compare a variable with files in a directory and output the equals
I am making a bash script where I want to find files that are equal to a variable. The equals will then be used.
I want to use "mogrify" to shrink a couple of image files that have the same name as the ones i gather from a list (similar to "dpkg -l"). It is not "dpkg -l" I am using but it is similar. My problem is that it prints all the files not just the equals. I am pretty sure this could be done with awk instead of a for-loop but I do not know how.
prog="`dpkg -l | awk '{print $1}'`"
for file in $dirone* $dirtwo*
do
if [ "basename ${file}" = "${prog}" ]; then
echo ${file} are equal
else
echo ${file} are not equal
fi
done
C开发者_StackOverflow社区ould you please help me get this working?
First, I think there's a small typo. if [ "basename ${file}" =...
should have backticks inside the double quotes, just like the prog=...
line at the top does.
Second, if $prog
is a multi-line string (like dpkg -l
) you can't really compare a filename to the entire list. Instead you have to compare one item at a time to the filename.
Here's an example using dpkg
and /usr/bin
#!/bin/bash
progs="`dpkg -l | awk '{print $2}'`"
for file in /usr/bin/*
do
base=`basename ${file}`
for prog in ${progs}
do
if [ "${base}" = "${prog}" ]; then
echo "${file}" matches "${prog}"
fi
done
done
The condition "$file = $prog"
is a single string. You should try "$file" = "$prog"
instead.
The following transcript shows the fix:
pax> ls -1 qq*
qq
qq.c
qq.cpp
pax> export xx=qq.cpp
pax> for file in qq* ; do
if [[ "${file} = ${xx}" ]] ; then
echo .....${file} equal
else
echo .....${file} not equal
fi
done
.....qq equal
.....qq.c equal
.....qq.cpp equal
pax> for file in qq* ; do
if [[ "${file}" = "${xx}" ]] ; then
echo .....${file} equal
else
echo .....${file} not equal
fi
done
.....qq not equal
.....qq.c not equal
.....qq.cpp equal
You can see in the last bit of output that only qq.cpp
is shown as equal since it's the only one that matches ${xx}
.
The reason you're getting true is because that's what non-empty strings will give you:
pax> if [[ "" ]] ; then
echo .....equal
fi
pax> if [[ "x" ]] ; then
echo .....equal
fi
.....equal
That's because that form is the string length checking variation. From the bash
manpage under CONDITIONAL EXPRESSIONS
:
string
-n string
True if the length of string is non-zero.
Update:
The new code in your question won't quite work as expected. You need:
if [[ "$(basename ${file})" = "${prog}" ]]; then
to actually execute basename
and use its output as the first part of the equality check.
you can use case/esac
case "$file" in
"$prog" ) echo "same";;
esac
精彩评论