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I'm currently working on a project called 'dmCLI' which means 'download manager command line interface'. I'm using curl to multi-part download a file. And I'm having trouble with my code. I can't convert string to int.
Here's my full code. I also uploaded my code into Github Repo. Here it is:
dmCLI GitHub Repository
#!/bin/bash
RED='33[0;31m'
NC='33[0m'
help()
echo "dmcli [ FILENAME:path ] [ URL:uri ]"
echo -e "author: $RED@atahabaki$NC"
echo -e " __ _______ ____"
echo -e " ___/ /_ _ / ___/ / / _/"
echo -e "/ _ / ' / /__/ /___/ / "
echo -e "_,_/_/_/_/___/____/___/ "
echo -e " "
echo -e "$REDDownloading$NC has never been $REDeasier$NC.n"
if [ $# == 2 ]
then
filename=$1;
url=$2
headers=`curl -I $url > headers`
contentlength=`cat headers | grep -E '[Cc]ontent-[Ll]ength:' | sed 's/[Cc]ontent-[Ll]ength:[ ]*//g'`
acceptranges=`cat headers | grep -E '[Aa]ccept-[Rr]anges:' | sed 's/[Aa]ccept-[Rr]anges:[ ]*//g'`
echo -e 'n'
if [ "$acceptranges" = "bytes" ]
then
echo File does not allow multi-part download.
else
echo File allows multi-part download.
fi
echo "$(($contentlength + 9))"
# if [acceptranges == 'bytes']
# then
# divisionresult = $((contentlength/9))
# use for to create ranges...
else
help
fi
# First get Content-Length via regex or request,
# Then Create Sequences,
# After Start Downloading,
# Finally, re-assemble to 1 file.
I want to divide contentlength's value by 9. I tried this:
echo "$(($contentlength/9))"
It's getting below error:
/9")syntax error: invalid arithmetic operator (error token is "
I'm using localhost written in node.js. I added head responses. It returns Content-Length of the requested file, and the above dmCLI.sh gets correctly the Content-Length value.
./dmcli.sh home.html http://127.0.0.1:404/
A HEAD request to http://127.0.0.1:404/ returns: Content-Length: 283, Accept-Range: bytes
The dmCLI works for getting the value, but when I want to access its value, it won't work.
Simple actions work like:
echo "$contentlength"
But I can't access it by using this:
echo "$contentlength bytes"
and here:
echo "$(($contentlength + 9))"
returns 9 but I'm expecting 292. Where's the problem; why is it not working?
shell-script numeric-data arithmetic
edited yesterday
Jeff Schaller
43.8k1161141
asked Mar 14 at 9:25
A. Taha BakiA. Taha Baki
133
|
show 2 more comments
I'm currently working on a project called 'dmCLI' which means 'download manager command line interface'. I'm using curl to multi-part download a file. And I'm having trouble with my code. I can't convert string to int.
Here's my full code. I also uploaded my code into Github Repo. Here it is:
dmCLI GitHub Repository
#!/bin/bash
RED='33[0;31m'
NC='33[0m'
help()
echo "dmcli [ FILENAME:path ] [ URL:uri ]"
echo -e "author: $RED@atahabaki$NC"
echo -e " __ _______ ____"
echo -e " ___/ /_ _ / ___/ / / _/"
echo -e "/ _ / ' / /__/ /___/ / "
echo -e "_,_/_/_/_/___/____/___/ "
echo -e " "
echo -e "$REDDownloading$NC has never been $REDeasier$NC.n"
if [ $# == 2 ]
then
filename=$1;
url=$2
headers=`curl -I $url > headers`
contentlength=`cat headers | grep -E '[Cc]ontent-[Ll]ength:' | sed 's/[Cc]ontent-[Ll]ength:[ ]*//g'`
acceptranges=`cat headers | grep -E '[Aa]ccept-[Rr]anges:' | sed 's/[Aa]ccept-[Rr]anges:[ ]*//g'`
echo -e 'n'
if [ "$acceptranges" = "bytes" ]
then
echo File does not allow multi-part download.
else
echo File allows multi-part download.
fi
echo "$(($contentlength + 9))"
# if [acceptranges == 'bytes']
# then
# divisionresult = $((contentlength/9))
# use for to create ranges...
else
help
fi
# First get Content-Length via regex or request,
# Then Create Sequences,
# After Start Downloading,
# Finally, re-assemble to 1 file.
I want to divide contentlength's value by 9. I tried this:
echo "$(($contentlength/9))"
It's getting below error:
/9")syntax error: invalid arithmetic operator (error token is "
I'm using localhost written in node.js. I added head responses. It returns Content-Length of the requested file, and the above dmCLI.sh gets correctly the Content-Length value.
./dmcli.sh home.html http://127.0.0.1:404/
A HEAD request to http://127.0.0.1:404/ returns: Content-Length: 283, Accept-Range: bytes
The dmCLI works for getting the value, but when I want to access its value, it won't work.
Simple actions work like:
echo "$contentlength"
But I can't access it by using this:
echo "$contentlength bytes"
and here:
echo "$(($contentlength + 9))"
returns 9 but I'm expecting 292. Where's the problem; why is it not working?
shell-script numeric-data arithmetic
edited yesterday
Jeff Schaller
43.8k1161141
asked Mar 14 at 9:25
A. Taha BakiA. Taha Baki
133
Ifecho "$contentlength"works, there is no reasonecho "$contentlength bytes"does not work as well.
– Weijun Zhou
Mar 14 at 9:32
2
Could be the value of the variable ends in a CR character (line delimiters in HTTP headers are CRLF),12345r byteswould show up as" bytes"in a terminal as CR moves the cursor to the beginning of the line.
– Stéphane Chazelas
Mar 14 at 9:34
@StéphaneChazelas You're right.CRdoes not have this behavior when redirected. One can redirect the output and examine the result.
– Weijun Zhou
Mar 14 at 9:36
echo " $contentlength bytes"it returns this: ``` bytes```
– A. Taha Baki
Mar 14 at 9:38
The way it's written (not proper header parsing, no sanitisation of the content length), this script has an arbitrary command injection vulnerability. Do not use a shell for this kind of thing. perl/python have HTTP or libcurl APIs.
– Stéphane Chazelas
Mar 14 at 9:38
|
show 2 more comments
I'm currently working on a project called 'dmCLI' which means 'download manager command line interface'. I'm using curl to multi-part download a file. And I'm having trouble with my code. I can't convert string to int.
Here's my full code. I also uploaded my code into Github Repo. Here it is:
dmCLI GitHub Repository
#!/bin/bash
RED='33[0;31m'
NC='33[0m'
help()
echo "dmcli [ FILENAME:path ] [ URL:uri ]"
echo -e "author: $RED@atahabaki$NC"
echo -e " __ _______ ____"
echo -e " ___/ /_ _ / ___/ / / _/"
echo -e "/ _ / ' / /__/ /___/ / "
echo -e "_,_/_/_/_/___/____/___/ "
echo -e " "
echo -e "$REDDownloading$NC has never been $REDeasier$NC.n"
if [ $# == 2 ]
then
filename=$1;
url=$2
headers=`curl -I $url > headers`
contentlength=`cat headers | grep -E '[Cc]ontent-[Ll]ength:' | sed 's/[Cc]ontent-[Ll]ength:[ ]*//g'`
acceptranges=`cat headers | grep -E '[Aa]ccept-[Rr]anges:' | sed 's/[Aa]ccept-[Rr]anges:[ ]*//g'`
echo -e 'n'
if [ "$acceptranges" = "bytes" ]
then
echo File does not allow multi-part download.
else
echo File allows multi-part download.
fi
echo "$(($contentlength + 9))"
# if [acceptranges == 'bytes']
# then
# divisionresult = $((contentlength/9))
# use for to create ranges...
else
help
fi
# First get Content-Length via regex or request,
# Then Create Sequences,
# After Start Downloading,
# Finally, re-assemble to 1 file.
I want to divide contentlength's value by 9. I tried this:
echo "$(($contentlength/9))"
It's getting below error:
/9")syntax error: invalid arithmetic operator (error token is "
I'm using localhost written in node.js. I added head responses. It returns Content-Length of the requested file, and the above dmCLI.sh gets correctly the Content-Length value.
./dmcli.sh home.html http://127.0.0.1:404/
A HEAD request to http://127.0.0.1:404/ returns: Content-Length: 283, Accept-Range: bytes
The dmCLI works for getting the value, but when I want to access its value, it won't work.
Simple actions work like:
echo "$contentlength"
But I can't access it by using this:
echo "$contentlength bytes"
and here:
echo "$(($contentlength + 9))"
returns 9 but I'm expecting 292. Where's the problem; why is it not working?
shell-script numeric-data arithmetic
edited yesterday
Jeff Schaller
43.8k1161141
asked Mar 14 at 9:25
A. Taha BakiA. Taha Baki
133
I'm currently working on a project called 'dmCLI' which means 'download manager command line interface'. I'm using curl to multi-part download a file. And I'm having trouble with my code. I can't convert string to int.
Here's my full code. I also uploaded my code into Github Repo. Here it is:
dmCLI GitHub Repository
#!/bin/bash
RED='33[0;31m'
NC='33[0m'
help()
echo "dmcli [ FILENAME:path ] [ URL:uri ]"
echo -e "author: $RED@atahabaki$NC"
echo -e " __ _______ ____"
echo -e " ___/ /_ _ / ___/ / / _/"
echo -e "/ _ / ' / /__/ /___/ / "
echo -e "_,_/_/_/_/___/____/___/ "
echo -e " "
echo -e "$REDDownloading$NC has never been $REDeasier$NC.n"
if [ $# == 2 ]
then
filename=$1;
url=$2
headers=`curl -I $url > headers`
contentlength=`cat headers | grep -E '[Cc]ontent-[Ll]ength:' | sed 's/[Cc]ontent-[Ll]ength:[ ]*//g'`
acceptranges=`cat headers | grep -E '[Aa]ccept-[Rr]anges:' | sed 's/[Aa]ccept-[Rr]anges:[ ]*//g'`
echo -e 'n'
if [ "$acceptranges" = "bytes" ]
then
echo File does not allow multi-part download.
else
echo File allows multi-part download.
fi
echo "$(($contentlength + 9))"
# if [acceptranges == 'bytes']
# then
# divisionresult = $((contentlength/9))
# use for to create ranges...
else
help
fi
# First get Content-Length via regex or request,
# Then Create Sequences,
# After Start Downloading,
# Finally, re-assemble to 1 file.
I want to divide contentlength's value by 9. I tried this:
echo "$(($contentlength/9))"
It's getting below error:
/9")syntax error: invalid arithmetic operator (error token is "
I'm using localhost written in node.js. I added head responses. It returns Content-Length of the requested file, and the above dmCLI.sh gets correctly the Content-Length value.
./dmcli.sh home.html http://127.0.0.1:404/
A HEAD request to http://127.0.0.1:404/ returns: Content-Length: 283, Accept-Range: bytes
The dmCLI works for getting the value, but when I want to access its value, it won't work.
Simple actions work like:
echo "$contentlength"
But I can't access it by using this:
echo "$contentlength bytes"
and here:
echo "$(($contentlength + 9))"
returns 9 but I'm expecting 292. Where's the problem; why is it not working?
shell-script numeric-data arithmetic
shell-script numeric-data arithmetic
edited yesterday
Jeff Schaller
43.8k1161141
asked Mar 14 at 9:25
A. Taha BakiA. Taha Baki
133
edited yesterday
Jeff Schaller
43.8k1161141
asked Mar 14 at 9:25
A. Taha BakiA. Taha Baki
133
edited yesterday
Jeff Schaller
43.8k1161141
edited yesterday
Jeff Schaller
43.8k1161141
edited yesterday
Jeff Schaller
43.8k1161141
43.8k1161141
asked Mar 14 at 9:25
A. Taha BakiA. Taha Baki
133
asked Mar 14 at 9:25
A. Taha BakiA. Taha Baki
133
asked Mar 14 at 9:25
A. Taha BakiA. Taha Baki
133
133
Ifecho "$contentlength"works, there is no reasonecho "$contentlength bytes"does not work as well.
– Weijun Zhou
Mar 14 at 9:32
2
Could be the value of the variable ends in a CR character (line delimiters in HTTP headers are CRLF),12345r byteswould show up as" bytes"in a terminal as CR moves the cursor to the beginning of the line.
– Stéphane Chazelas
Mar 14 at 9:34
@StéphaneChazelas You're right.CRdoes not have this behavior when redirected. One can redirect the output and examine the result.
– Weijun Zhou
Mar 14 at 9:36
echo " $contentlength bytes"it returns this: ``` bytes```
– A. Taha Baki
Mar 14 at 9:38
The way it's written (not proper header parsing, no sanitisation of the content length), this script has an arbitrary command injection vulnerability. Do not use a shell for this kind of thing. perl/python have HTTP or libcurl APIs.
– Stéphane Chazelas
Mar 14 at 9:38
|
show 2 more comments
Ifecho "$contentlength"works, there is no reasonecho "$contentlength bytes"does not work as well.
– Weijun Zhou
Mar 14 at 9:32
2
Could be the value of the variable ends in a CR character (line delimiters in HTTP headers are CRLF),12345r byteswould show up as" bytes"in a terminal as CR moves the cursor to the beginning of the line.
– Stéphane Chazelas
Mar 14 at 9:34
@StéphaneChazelas You're right.CRdoes not have this behavior when redirected. One can redirect the output and examine the result.
– Weijun Zhou
Mar 14 at 9:36
echo " $contentlength bytes"it returns this: ``` bytes```
– A. Taha Baki
Mar 14 at 9:38
The way it's written (not proper header parsing, no sanitisation of the content length), this script has an arbitrary command injection vulnerability. Do not use a shell for this kind of thing. perl/python have HTTP or libcurl APIs.
– Stéphane Chazelas
Mar 14 at 9:38
If
echo "$contentlength" works, there is no reason echo "$contentlength bytes" does not work as well.– Weijun Zhou
Mar 14 at 9:32
If
echo "$contentlength" works, there is no reason echo "$contentlength bytes" does not work as well.– Weijun Zhou
Mar 14 at 9:32
2
2
Could be the value of the variable ends in a CR character (line delimiters in HTTP headers are CRLF),
12345r bytes would show up as " bytes" in a terminal as CR moves the cursor to the beginning of the line.– Stéphane Chazelas
Mar 14 at 9:34
Could be the value of the variable ends in a CR character (line delimiters in HTTP headers are CRLF),
12345r bytes would show up as " bytes" in a terminal as CR moves the cursor to the beginning of the line.– Stéphane Chazelas
Mar 14 at 9:34
@StéphaneChazelas You're right.
CR does not have this behavior when redirected. One can redirect the output and examine the result.– Weijun Zhou
Mar 14 at 9:36
@StéphaneChazelas You're right.
CR does not have this behavior when redirected. One can redirect the output and examine the result.– Weijun Zhou
Mar 14 at 9:36
echo " $contentlength bytes" it returns this: ``` bytes```– A. Taha Baki
Mar 14 at 9:38
echo " $contentlength bytes" it returns this: ``` bytes```– A. Taha Baki
Mar 14 at 9:38
The way it's written (not proper header parsing, no sanitisation of the content length), this script has an arbitrary command injection vulnerability. Do not use a shell for this kind of thing. perl/python have HTTP or libcurl APIs.
– Stéphane Chazelas
Mar 14 at 9:38
The way it's written (not proper header parsing, no sanitisation of the content length), this script has an arbitrary command injection vulnerability. Do not use a shell for this kind of thing. perl/python have HTTP or libcurl APIs.
– Stéphane Chazelas
Mar 14 at 9:38
|
show 2 more comments
2 Answers
2
active
oldest
votes
The regex below will extract the number of bytes, only the number:
contentlength=$(
LC_ALL=C sed '
/^[Cc]ontent-[Ll]ength:[[:blank:]]*0*([0-9]1,).*$/!d
s//1/; q' headers
)
After the above change, the contentlength variable will be only made of decimal digits (with leading 0s removes so the shell doesn't consider the number as octal), thus the 2 lines below will display the same result:
echo "$(($contentlength/9))"
echo "$((contentlength/9))"
edited Mar 14 at 10:50
Stéphane Chazelas
311k57587945
answered Mar 14 at 9:46
Jay jargotJay jargot
97138
It worked but what's the difference betweenecho $((contentlength/9))andecho $(($contentlength))?
– A. Taha Baki
Mar 14 at 9:51
I won't call$(($contentlength/9))incorrect, just that the$is unnecessary, but there are cases where this$is needed.
– Weijun Zhou
Mar 14 at 9:57
There will beARITHMETIC EVALUATIONwith this syntax, you can read this in theman bash:Within an expression, shell variables may also be referenced by name without using the parameter expansion syntax.. In other words: do not use$for variable with this syntax.
– Jay jargot
Mar 14 at 9:58
1
But what if parameter expansion is needed?$in$(($b/5/7+1))is needed.
– Weijun Zhou
Mar 14 at 10:00
1
@Jayjargot, there will be arithmetic evaluation with both syntax in ksh, bash and zsh (hence the command injection vulnerabilities when the input is not sanitized), one difference is when the value is like9+9. Thencontentlength/9will give 2 and$contentlength/9will give 1.
– Stéphane Chazelas
Mar 14 at 10:01
|
show 7 more comments
headers=`curl -I $url > headers`
contentlength=`cat headers | grep -E '[Cc]ontent-[Ll]ength:' | sed 's/[Cc]ontent-[Ll]ength:[ ]*//g'`
echo "$(($contentlength/9))"
It's getting below error:
/9")syntax error: invalid arithmetic operator (error token is "
HTTP headers always end with CR/LF, not just LF; your `cat headers | ...` command expansion will remove the ending LF, but leave the CR alone, which will cause that strange error.
% var=`printf "%srn" 333`command expansion will remove the ending LF, but leave the CR alone, which will cause that strange error.
% echo var=$var
}ar= ...`% var=`printf "%srn" 333`
% echo var=$var
ar=
headers=`curl -I $url > headers`
contentlength=`cat headers ar= sed 's/[Cc]ontent-[Ll]ength:[ ]*//g'`
echo "$(($contentlength/9))"
It's getting below error:
/9")syntax error: invalid arithmetic operator (error token is "
HTTP headers always end with CR/LF, not just LF; your `cat headers ar= ...` command expansion will remove the ending LF, but leave the CR alone, which will cause that strange error.
% var=`printf "%srn" 333`
% echo var=$var
ar={333
% echo "$((var / 3))"
")syntax error: invalid arithmetic operator (error token is "
answered yesterday
pizdelectpizdelect
70929
answered yesterday
pizdelectpizdelect
70929
answered yesterday
pizdelectpizdelect
70929
answered yesterday
pizdelectpizdelect
70929
70929
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If
echo "$contentlength"works, there is no reasonecho "$contentlength bytes"does not work as well.– Weijun Zhou
Mar 14 at 9:32
2
Could be the value of the variable ends in a CR character (line delimiters in HTTP headers are CRLF),
12345r byteswould show up as" bytes"in a terminal as CR moves the cursor to the beginning of the line.– Stéphane Chazelas
Mar 14 at 9:34
@StéphaneChazelas You're right.
CRdoes not have this behavior when redirected. One can redirect the output and examine the result.– Weijun Zhou
Mar 14 at 9:36
echo " $contentlength bytes"it returns this: ``` bytes```– A. Taha Baki
Mar 14 at 9:38
The way it's written (not proper header parsing, no sanitisation of the content length), this script has an arbitrary command injection vulnerability. Do not use a shell for this kind of thing. perl/python have HTTP or libcurl APIs.
– Stéphane Chazelas
Mar 14 at 9:38