A regular expression in JavaScript to extract a file name from the Content-Disposition header

Question

A regular expression in JavaScript to extract a file name from the Content-Disposition header

The Content-disposition header often contains a filename that may have different formatting, such as with double quotes or no quotes. Is there a regex pattern that can successfully extract the filename in all these cases?

Content-Disposition: attachment; filename=content.txt

Here are some examples of possible variations:

attachment; filename=content.txt
attachment; filename*=UTF-8''filename.txt
attachment; filename="EURO rates"; filename*=utf-8''%e2%82%ac%20rates
attachment; filename="omáèka.jpg"
and other combinations could also exist

javascript regex

Answer 1

Answer №1

Here is a suggestion you might consider:

fileTitle[^;=\n]*=((['"]).*?\2|[^;\n]*)

fileTitle      # locate fileTitle, followed by
[^;=\n]*       # any character that is not a semicolon, equals sign, or newline
=
(              # starting the first capture group
    (['"])     # either a single or double quote, enclosed in the second capturing group
    .*?        # anything until the first...
    \2         # matching quote (single if found initially or double later)
|              # Alternatively,
    [^;\n]*    # any character except for a semicolon or newline
)

The filename you are seeking is within the initial capturing group: http://regex101.com/r/oD9jK4

Answer 2

Here is a suggestion you might consider:

fileTitle[^;=\n]*=((['"]).*?\2|[^;\n]*)

fileTitle      # locate fileTitle, followed by
[^;=\n]*       # any character that is not a semicolon, equals sign, or newline
=
(              # starting the first capture group
    (['"])     # either a single or double quote, enclosed in the second capturing group
    .*?        # anything until the first...
    \2         # matching quote (single if found initially or double later)
|              # Alternatively,
    [^;\n]*    # any character except for a semicolon or newline
)

The filename you are seeking is within the initial capturing group: http://regex101.com/r/oD9jK4

Answer 3

Answer №2

Adjusted slightly to suit my requirements (removes all quotation marks and special characters)

documentname\*?=['"]?(?:UTF-\d['"]*)?([^;\r\n"']*)['"]?;?

https://regex101.com/r/AcUzKy/4

Answer 4

Adjusted slightly to suit my requirements (removes all quotation marks and special characters)

documentname\*?=['"]?(?:UTF-\d['"]*)?([^;\r\n"']*)['"]?;?

https://regex101.com/r/AcUzKy/4

Answer 5

Answer №3

/regexPattern[^;=\n]*=(?:(\\?['"])(.*?)\1|(?:[^\s]+'.*?')?([^;\n]*))/i

https://regex101.com/r/eK4uP8/12

Update: Another option is to utilize this processor: https://github.com/AliceWD/open-in-browser/blob/master/extension/content-disposition.js

Answer 6

/regexPattern[^;=\n]*=(?:(\\?['"])(.*?)\1|(?:[^\s]+'.*?')?([^;\n]*))/i

https://regex101.com/r/eK4uP8/12

Update: Another option is to utilize this processor: https://github.com/AliceWD/open-in-browser/blob/master/extension/content-disposition.js

Answer 7

Answer №4

filename[^;\n]*=(UTF-\d['"]*)?((['"]).*?[.]$\2|[^;\n]*)?

I have enhanced Robin’s method to perform two additional tasks:

Now it can capture the filename even when it contains escaped double quotes. https://i.sstatic.net/JAoVj.png
This upgrade allows for capturing UTF-8'' section as a distinct group. https://i.sstatic.net/3CspZ.png

This particular solution is based on ECMAScript.

https://regex101.com/r/7Csdp4/3/

Answer 8

filename[^;\n]*=(UTF-\d['"]*)?((['"]).*?[.]$\2|[^;\n]*)?

I have enhanced Robin’s method to perform two additional tasks:

Now it can capture the filename even when it contains escaped double quotes. https://i.sstatic.net/JAoVj.png
This upgrade allows for capturing UTF-8'' section as a distinct group. https://i.sstatic.net/3CspZ.png

This particular solution is based on ECMAScript.

https://regex101.com/r/7Csdp4/3/

Answer 9

Answer №5

Important Note: Please be aware that this solution is specifically tailored for PCRE (e.g. Python / PHP). If you require a solution using JavaScript, I recommend referring to Robin's answer.

This adjusted rendition of Robin's regex effectively eliminates the quotes:

filename[^;\n=]*=(['\"])*(.*)(?(1)\1|)

filename        # matches "filename", followed by
[^;=\n]*        # any character except ;, =, or a newline
=
(['"])*         # either a single or double quote will be placed in capturing group 1
(?:utf-8\'\')?  # deletes the utf-8 section from the match
(.*)            # second capturing group, which will encompass the filename
(?(1)\1|)       # conditional statement: if first capturing group is not empty,
                # match it again (the quotes); otherwise, do not match anything

https://regex101.com/r/hJ7tS6/28

The filename can be found in the second capturing group.

Answer 10

Important Note: Please be aware that this solution is specifically tailored for PCRE (e.g. Python / PHP). If you require a solution using JavaScript, I recommend referring to Robin's answer.

This adjusted rendition of Robin's regex effectively eliminates the quotes:

filename[^;\n=]*=(['\"])*(.*)(?(1)\1|)

filename        # matches "filename", followed by
[^;=\n]*        # any character except ;, =, or a newline
=
(['"])*         # either a single or double quote will be placed in capturing group 1
(?:utf-8\'\')?  # deletes the utf-8 section from the match
(.*)            # second capturing group, which will encompass the filename
(?(1)\1|)       # conditional statement: if first capturing group is not empty,
                # match it again (the quotes); otherwise, do not match anything

https://regex101.com/r/hJ7tS6/28

The filename can be found in the second capturing group.

Answer 11

Answer №6

Check out the regex pattern I created for Javascript:

filename\*?=((['"])[\s\S]*?\2|[^;\n]*)

This regular expression was implemented in a recent project of mine.

Answer 12

Check out the regex pattern I created for Javascript:

filename\*?=((['"])[\s\S]*?\2|[^;\n]*)

This regular expression was implemented in a recent project of mine.

Answer 13

Answer №7

My latest accomplishment involves creating a regex pattern that efficiently captures these specified names by utilizing a designated group called filename

/(?<=filename(?:=|\*=(?:[\w\-]+'')))["']?(?<filename>[^"';\n]+)["']?/g

const regex = /(?<=filename(?:=|\*=(?:[\w\-]+'')))["']?(?<filename>[^"';\n]+)["']?/g

const filenames = `
attachment; filename=content.txt
attachment; filename*=UTF-8''filename.txt
attachment; filename="EURO rates"; filename*=utf-8''%e2%82%ac%20rates
attachment; filename="omáèka.jpg"
`

function logMatches(){
  const array = new Array

  filenames.split("\n").forEach(line => {
    if(!line.trim()) return

    const matches = line.matchAll(regex)
    const groups = Array.from(matches).map(match => match?.groups?.filename)

    array.push(groups.length === 1 ? groups[0] : groups)
  })

  console.log(array)
}

logMatches()

Answer 14

My latest accomplishment involves creating a regex pattern that efficiently captures these specified names by utilizing a designated group called filename

/(?<=filename(?:=|\*=(?:[\w\-]+'')))["']?(?<filename>[^"';\n]+)["']?/g

const regex = /(?<=filename(?:=|\*=(?:[\w\-]+'')))["']?(?<filename>[^"';\n]+)["']?/g

const filenames = `
attachment; filename=content.txt
attachment; filename*=UTF-8''filename.txt
attachment; filename="EURO rates"; filename*=utf-8''%e2%82%ac%20rates
attachment; filename="omáèka.jpg"
`

function logMatches(){
  const array = new Array

  filenames.split("\n").forEach(line => {
    if(!line.trim()) return

    const matches = line.matchAll(regex)
    const groups = Array.from(matches).map(match => match?.groups?.filename)

    array.push(groups.length === 1 ? groups[0] : groups)
  })

  console.log(array)
}

logMatches()

A regular expression in JavaScript to extract a file name from the Content-Disposition header

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

Answer №6

Answer №7

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