Linux · sockets & transfer

wget

download a file

wget fetches a URL and saves it as a file, under the name in the address. It is built for downloading: it retries, resumes a broken transfer, and can mirror a whole site.

curl prints a response to the screen; wget saves it to a file.

Saves to

A file

named from the URL

Resume

-c

continue a partial download

Rename

-O NAME

capital O

Follows

Redirects

by default

At the terminal

Read the session first, then the notes: each numbered line in the output is answered by the note with the same number.

user@netflow — bashwget

$ wget https://example.com/files/tool-1.4.tar.gz

1Resolving example.com (example.com)... 192.0.2.80

Connecting to example.com (example.com)|192.0.2.80|:443... connected.

2HTTP request sent, awaiting response... 200 OK

Length: 4821033 (4.6M) [application/gzip]

Saving to: 'tool-1.4.tar.gz'

3tool-1.4.tar.gz 100%[===================>] 4.60M 3.12MB/s in 1.5s

4$ sha256sum tool-1.4.tar.gz

9f2c1e…a41b tool-1.4.tar.gz

Illustrative session · names, sizes and dates are examples, and every address is from a documentation or private range

Reading the output

What the numbered lines are telling you

DNS, then TCP

The name is resolved and a connection opened to port 443 — the same steps any HTTPS client takes.

The server’s answer

200 OK, followed by the size and type of what is about to arrive.

The progress bar

Percentage, bytes received, speed and time. The file is saved in the current directory.

Check what you got

Compare the checksum with the one the publisher lists. If they differ, the file is corrupt or not what it claims to be.

Switches

A switch changes how the command behaves. These are the ones used day to day; man wget lists the rest. Single-letter switches can usually be joined, so -l -a may be written -la.

-O FILE: Save under this name. "-O -" writes to standard output.
-c: Continue a partially downloaded file.
-q: Quiet: no progress output.
-P DIR: Save into this directory.
-i FILE: Read URLs from a file.
-r: Recursive: follow links and download what they point to.
--limit-rate=RATE: Limit the download speed, such as 500k.
-b: Go to the background straight after starting.

Variations worth knowing

The same tool, pointed at a narrower question. These four cover most of what it is reached for day to day.

wget -c https://example.com/big.iso

Resumes a download that was cut off.

wget -O latest.tar.gz https://example.com/download

Saves under a name of your choosing.

wget -q -O - https://example.com/install.sh | less

Sends the download to a pager instead of a file, to read it first.

wget -i urls.txt

Downloads every URL listed in a file.

In cybersecurity

A downloaded file is someone else’s code arriving on your machine.

Verify before you run

Check the SHA-256 checksum or GPG signature against the publisher’s. HTTPS proves which server you reached, not that the file is the right one.

Never pipe straight to a shell

"wget -O - url | sh" runs whatever the server sends, unseen. Download it, read it, then run it.

Leave certificate checking on

--no-check-certificate makes the download open to interception. Fix the certificate problem instead.

Protocols it shows

HTTP TLS TCP DNS FTP

Read alongside

curlMakes one request over HTTP, HTTPS or a dozen other protocols and shows every stage — the connection, the TLS handshake, the headers.tarPacks a directory tree into a single archive file, and unpacks it again — optionally compressed.