Here is a quick tip, if you wish to perform an unattended download of large files such as Linux DVD ISO image file use the wget command.

Syntax

The syntax is as follows for a non-interactive download:
wget -bqc http://path-to-url/linux.iso
You will see a PID on screen:

Continuing in background, pid 12345.

Where,

• -b : Go to background immediately after startup. If no output file is specified via the -o, output is redirected to wget-log.
• -q : Turn off wget’s output aka save disk space.
• -c : Resume broken download i.e. continue getting a partially-downloaded file. This is useful when you want to finish up a download started by a previous instance of wget, or by another program.

Examples

This tip will save your time while downloading large ISO file or any other files from the Internets:

## download a large file in background ##
wget -bqc  http://bay.uchicago.edu/centos/7.0.1406/isos/x86_64/CentOS-7.0-1406-x86_64-DVD.iso
 
## Verify it ##
ps aux | grep wget
ls -lh CentOS-7.0-1406-x86_64-DVD.iso
 
## [Optional] Stop download by killing by PID number
kill PID-HERE
ps aux | grep wget

Sample session from above commands:

The nohup command

You can also use the nohup command to execute commands after you exit from a shell prompt. The syntax is:

$ nohup wget -qc http://path-to-url/linux.iso &
 
## exit from shell or close the terminal ##
$ exit

The disown bash command

Another option is to use the disown command as follows:

$ wget -qc http://path-to-url/linux.iso &
[1] 10685
$ disown wget
$ ps
  PID TTY          TIME CMD
10685 pts/0    00:00:00 wget
10687 pts/0    00:00:00 bash
10708 pts/0    00:00:00 ps
$ logout

See disown command examples for more info.

The screen command

You can also use the screen command which is a full-screen window manager that multiplexes a physical terminal between several processes (typically interactive shells).

See also

• Linux: wget your ultimate command line downloader
• Man pages – wget(1),nohup(1),bash(1)

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