How to get file from POST data in Bash CGI script?

as long as you're always uploading exactly 1 file using the multipart/form-data format and the client always put the Content-Type as the last header of the file upload (which curl always seem to do), this seem to work:

#!/bin/bash

echo "Content-type: text/html"
echo ""

echo '<html>'
echo '<head>'
echo '<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">'
echo '<title>Foo</title>'
echo '</head>'
echo '<body>'

echo "<p>Start</p>"

if [ "$REQUEST_METHOD" = "POST" ]; then
    echo "<p>Post Method</p>"
    if [ "$CONTENT_LENGTH" -gt 0 ]; then
    in_raw="$(cat)"
    boundary=$(echo -n "$in_raw" | head -1 | tr -d '\r\n');
    filename=$(echo -n "$in_raw" | grep --text --max-count=1 -oP "(?<=filename=\")[^\"]*");
    file_content=$(echo -n "$in_raw" | sed '1,/Content-Type:/d' | tail -c +3 | head --lines=-1 | head --bytes=-4  );
    echo "boundary: $boundary"
    echo "filename: $filename"
    #echo "file_content: $file_content"
    fi
fi
echo '</body>'
echo '</html>'

exit 0

example upload invocation (which I used to debug the above):

curl http://localhost:81/cgi-bin/wtf.sh -F "[email protected]"
  • with all that said, THIS IS INSANITY! bash is absolutely not suitable for handling binary data, such as http file uploads, use something else. (PHP? Python? Perl?)

The ways curl sends data

With fields:

curl --data "param1=value1&param2=value2" https://example.com/resource.cgi

With fields specified individually:

curl --data "param1=value1" --data "param2=value2" https://example.com/resource.cgi

Multipart:

curl --form "[email protected]" https://example.com/resource.cgi

Multipart with fields and a filename:

curl --form "[email protected];filename=desired-filename.txt" --form param1=value1 --form param2=value2 https://example.com/resource.cgi

For a RESTful HTTP POST containing XML:

curl -X POST -d @filename.txt http://example.com/path/to/resource --header "Content-Type:text/xml"

or for JSON, use this:

curl -X POST -d @filename.txt http://example.com/path/to/resource --header "Content-Type:application/json"

This will read the contents of the file named filename.txt and send it as the post request.

For further information see

  • Manual -- curl usage explained
  • The cURL tutorial on emulating a web browser

Reading HTTP POST data using BASH

How to get the content length:

if [ "$REQUEST_METHOD" = "POST" ]; then
    if [ "$CONTENT_LENGTH" -gt 0 ]; then
        read -n $CONTENT_LENGTH POST_DATA <&0
        echo "$CONTENT_LENGTH"
    fi
fi

To save a binary or text file:

boundary=$(export | \
    sed '/CONTENT_TYPE/!d;s/^.*dary=//;s/.$//')
filename=$(echo "$QUERY_STRING" | \
    sed -n '2!d;s/\(.*filename=\"\)\(.*\)\".*$/\2/;p')
file=$(echo "$QUERY_STRING" | \
    sed -n "1,/$boundary/p" | sed '1,4d;$d')

The uploaded file is now contained in the $file variable, and file name in the $filename variable.

Tags:

Bash

Curl

Cgi

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