Curl Dump Response Headers to STDOUT and Ignore Response Body

Goals

Return only HTTP response header when opening a web page using curl. This is useful when we are interested in processing response headers only.

Command

We will utilize /dev/stdout and /dev/null to achieve what we want.

$ curl https://notes.rioastamal.net -D /dev/stdout -o /dev/null --silent
HTTP/2 200
date: Sun, 06 May 2018 23:42:37 GMT
content-type: text/html; charset=UTF-8
set-cookie: __cfduid=d6347d57f364b276150034b241b19cdb01525650157; expires=Mon, 06-May-19 23:42:37 GMT; path=/; domain=.rioastamal.net; HttpOnly
expires: Sun, 06 May 2018 23:42:37 GMT
cache-control: private, max-age=0
last-modified: Sun, 06 May 2018 23:42:05 GMT
x-content-type-options: nosniff
x-xss-protection: 1; mode=block
expect-ct: max-age=604800, report-uri="https://report-uri.cloudflare.com/cdn-cgi/beacon/expect-ct"
server: cloudflare
cf-ray: 416f4deb6f51a320-HKG

Reference

• https://unix.stackexchange.com/questions/16357/usage-of-dash-in-place-of-a-filename

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Generate Random String in Shell Using /dev/urandom

Goals

Generate random string in Shell and using /dev/urandom as the source. This random string typically useful to be used as encryption key.

Implementation

We will use combination of tr and head to generate 32 random characters. Command below will only output alphanumeric and some characters symbol only.

$ </dev/urandom tr -dc 'A-Za-z0-9!"#$%&()*+,-./:;<=>?@[\]^_`{|}~' | head -c 32 && echo
}s9s2c8W7aZlI:yg<{bg&-<7YnyJEk.u

On Mac OS X system you may need to define LC_ALL=C environment variable as shown below.

$ LC_ALL=C </dev/urandom tr -dc 'A-Za-z0-9!"#$%&()*+,-./:;<=>?@[\]^_`{|}~' | head -c 32 && echo
f(s_TPj*.H3Z/s[*:zLe[=9&0$FF"*8[

References

• https://www.howtogeek.com/howto/30184/10-ways-to-generate-a-random-password-from-the-command-line/
• https://unix.stackexchange.com/questions/230673/how-to-generate-a-random-string

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How to Flatten Multidimensional Array in PHP

Goals

Turn PHP multi-dimensional array into one dimensional array (Flatten).

Solution

We will use Standard PHP Library (SPL) to tackle the problem. Assume we have an array like below.

$origin = [
    'Level 1',
    '_2_' => [
        'Level 2',
        '_3_' => [
            'Level 3',
            '_4_' => [
                'Level 4',
                '_5_' => [
                    'Level 5'
                 ]
            ]
        ]
   ],
   'Another Level 1',
   '_2_1' => [
       'Another Level 2'
   ]
];

Turn it into one dimensional array by using SPL RecursiveIteratorIterator and RecursiveArrayIterator class.

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