String to integer in Shell

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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?

edited Mar 24 at 13:42

Jeff Schaller♦

45k1164147

asked Mar 14 at 9:25

A. Taha Baki

133

If echo "$contentlength" works, there is no reason echo "$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 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

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

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?

edited Mar 24 at 13:42

Jeff Schaller♦

45k1164147

asked Mar 14 at 9:25

A. Taha Baki

133

If echo "$contentlength" works, there is no reason echo "$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 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

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

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?

edited Mar 24 at 13:42

Jeff Schaller♦

45k1164147

asked Mar 14 at 9:25

A. Taha Baki

133

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 Mar 24 at 13:42

Jeff Schaller♦

45k1164147

asked Mar 14 at 9:25

A. Taha Baki

133

edited Mar 24 at 13:42

Jeff Schaller♦

45k1164147

asked Mar 14 at 9:25

A. Taha Baki

133

edited Mar 24 at 13:42

Jeff Schaller♦

45k1164147

edited Mar 24 at 13:42

Jeff Schaller♦

45k1164147

edited Mar 24 at 13:42

Jeff Schaller♦

45k1164147

asked Mar 14 at 9:25

A. Taha Baki

133

asked Mar 14 at 9:25

A. Taha Baki

133

asked Mar 14 at 9:25

A. Taha Baki

133

If echo "$contentlength" works, there is no reason echo "$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 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

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

If echo "$contentlength" works, there is no reason echo "$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 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

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

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

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

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

314k57594952

answered Mar 14 at 9:46

Jay jargot

97138

It worked but what's the difference between echo $((contentlength/9)) and echo $(($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 be ARITHMETIC EVALUATION with this syntax, you can read this in the man 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 like 9+9. Then contentlength/9 will give 2 and $contentlength/9 will 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`
% echo var=$var
}ar=improve this answer

edited Mar 14 at 10:50

Stéphane Chazelas

314k57594952

answered Mar 14 at 9:46

Jay jargot

97138

It worked but what's the difference between echo $((contentlength/9)) and echo $(($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 be ARITHMETIC EVALUATION with this syntax, you can read this in the man 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 like 9+9. Then contentlength/9 will give 2 and $contentlength/9 will give 1.

– Stéphane Chazelas
Mar 14 at 10:01

ar=improve this answer

answered Mar 24 at 14:56

pizdelect

767210

add a comment ar=

headers=`curl -I $url > headers`
contentlength=`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 Mar 24 at 14:56

pizdelect

767210

answered Mar 24 at 14:56

pizdelect

767210

answered Mar 24 at 14:56

pizdelect

767210

answered Mar 24 at 14:56

pizdelect

767210

add a comment |

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