Is it possible to read only first N bytes from the HTTP server using Linux command?

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8 Answers

usingpossiblefirst
90%

You can do it natively by the next curl command (no need to donwload whole document). According to culr man page:,Make a socket connection. Read the bytes you want. Close, and you're done. ,Given the url http://www.example.com, can we read the first N bytes out of the page?,You should also be aware that many HTTP/1.1 servers do not have this feature enabled, so that when you attempt to get a range, you'll instead get the whole document.

RANGES HTTP 1.1 introduced byte-ranges. Using this, a client can request to get only one or more subparts of a specified document. curl supports this with the -r flag.

Get the first 100 bytes of a document:
   curl - r 0 - 99 http: //www.get.this/

   Get the last 500 bytes of a document:
   curl - r - 500 http: //www.get.this/

   `curl`
also supports simple ranges
for FTP files as well.
Then you can only specify start and stop position.

Get the first 100 bytes of a document using FTP:
   curl - r 0 - 99 ftp: //www.get.this/README
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88%

Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers ,So the problem is that how can we read the first N bytes from the HTTP server in practice?,using urlib in python. similar question here, but according to Konstantin's comment, is that really true?,Thanks for contributing an answer to Stack Overflow!

RANGES HTTP 1.1 introduced byte-ranges. Using this, a client can request to get only one or more subparts of a specified document. curl supports this with the -r flag.

Get the first 100 bytes of a document:
   curl - r 0 - 99 http: //www.get.this/

   Get the last 500 bytes of a document:
   curl - r - 500 http: //www.get.this/

   `curl`
also supports simple ranges
for FTP files as well.
Then you can only specify start and stop position.

Get the first 100 bytes of a document using FTP:
   curl - r 0 - 99 ftp: //www.get.this/README
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72%

You can do this initially with the following curl command (no need to download the entire document). According to the culr man page:,You still need to get the whole network, so you can get a web with curls and, for example, connect it to your head.,You should also know that many HTTP / 1.1 servers do not have this feature enabled, so when you try to get a range, instead you get the whole document.,You should also be aware that this feature is not enabled on many HTTP / 1.1 servers, so when you try to get a range, you will get the whole document instead.

curl <url> | head -c 499

or

 curl <url> | dd bs=1 count=499

In addition, there are simpler utilities, perhaps borader availability, for example

  netcat host 80 << "HERE" | dd count = 499 of = output.fragment GET / urlpath / query ? string = more & bloddy = stuff HERE

Or

 GET / urlpath / query ? string = more & bloddy = stuff
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65%

The command you're looking for is head -n D where D can be any integer number. Example:, How can I overcome the setbacks of a negligent supervisor after earning a PhD degree? ,Asking for help, clarification, or responding to other answers., Are there any gaps in the range of gravitational wave frequencies we can detect?

The command you're looking for is head -n D where D can be any integer number. Example:

curl http: //example.com/123 | head -n 3
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75%

Pages that refer to this page: curl-config(1),  git-config(1),  mk-ca-bundle(1),  pmwebapi(3),  systemd-socket-proxyd(8) , For details of in-depth Linux/UNIX system programming training courses that I teach, look here.

40%

Without any option, it displays only the first 10 lines of the file specified. Example:  ,1. -n num: Prints the first ‘num’ lines instead of first 10 lines. num is mandatory to be specified in command otherwise it displays an error.  ,Cat command in Linux with examples,echo command in Linux with Examples

Syntax: 
 

head[OPTION]...[FILE]...
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22%

If the file does exist locally, Wget will first check its local time-stamp (similar to the way ls -l checks it), and then send a HEAD request to the remote server, demanding the information on the remote file. ,Several days later, you would like Wget to check if the remote file has changed, and download it if it has. ,Note that ‘-c’ only works with FTP servers and with HTTP servers that support the Range header. ,If this option is given, Wget will send Basic HTTP authentication information (plaintext username and password) for all requests, just like Wget 1.10.2 and prior did by default.

wget[option][URL]
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A CGI script is invoked by an HTTP server, usually to process user input submitted through an HTML <FORM> or <ISINDEX> element.,Print a list of useful (used by CGI) environment variables in HTML.,This module defines a number of utilities for use by CGI scripts written in Python.,Therefore, the appropriate way to read form data values was to always use the code which checks whether the obtained value is a single value or a list of values. That’s annoying and leads to less readable scripts.

print("Content-Type: text/html") # HTML is following
print() # blank line, end of headers
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