How to use SCP to transfer files in the macOS Terminal

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Earlier than private computer systems, there have been mainframe computer systems and timesharing terminals. Customers would log in to an account from a terminal to a mainframe, and situation instructions to the mainframe to course of.

Because the web got here of age within the Nineties the necessity arose to have the ability to use such terminal instructions securely throughout networks and computer systems. In 1994 a Finnish programmer named Tatu Ylonen created the Secure Shell. For background on utilizing Safe Shell, see our different SSH intro article.

As a part of the Safe Shell, the SCP (Secure Copy Protocol) program was created. SCP is each a protocol and a UNIX program which might be run from the Terminal command line in macOS.

SCP permits file transfers to and from SSH servers in each instructions. SCP is predicated on the RCP (Distant Copy) command (a part of BSD‘s r-commands) which was initially used when BSD got here to prominence within the mid 1980’s.

The default TCP port used for SCP file switch is 22 (the usual SSH port).

In contrast to different web requirements, there isn’t any RFC or formal customary for SCP – it is a part of the open-source OpenSSH project. You possibly can view all of OpenSSH’s supply code at its GitHub project.

To be able to use SCP to switch recordsdata, you could first set up an SSH connection through login to the distant server you want to switch recordsdata with. That is completed both by a username/password-based login in Terminal, or through using public key infrastructure (SSH PKI key pairs).

As soon as logged in to the distant server, you employ the ‘scp’ command adopted by choices in Terminal to switch recordsdata. There isn’t any strategy to receive listing listings utilizing scp, nor does it present a strategy to delete distant recordsdata, however you need to use customary UNIX filesystem instructions similar to ls to acquire listing listings as soon as logged in to the distant pc.

After an SSH connection is established, all instructions in that macOS Terminal window tab go to the server as a substitute of to your Mac.

For instance, within the macOS Terminal to get a listing itemizing of recordsdata on both the native machine or the distant server, you’ll be able to situation an ls command similar to:

The “-l” flag tells ls to checklist recordsdata vertically, within the Terminal window with every file/folder’s particulars similar to UNIX permissions, proprietor, group, measurement, and file creation date and time. Should you omit the “-l” flag, the ls command lists solely file names in a number of columns with out every file’s particulars.

For extra particulars on the ls command, in Terminal sort man ls and press Return.

To exit the person web page system in Terminal for any man web page, sort Management-Z and press Return.

It’s also possible to use the ‘cd’ (change listing) command to alter directories inside an area or distant file system. Merely sort ‘cd’ adopted by an area, and the identify or path of the listing you need to change to. All Terminal instructions then function on that listing, until you cd once more to a different listing or specify a full path in a command.

To go up one listing degree in a filesystem utilizing cd in Terminal, you’ll be able to sort:

To go to the very high (root) of a filesystem, sort:

You possibly can have Terminal print the present full path and listing identify in any filesystem by typing:

‘pwd’ is the UNIX command to get the current working listing (i.e. – the present listing the Terminal shell is working in). For the handbook web page on pwd in Terminal, sort:

See the scp man web page for extra particulars on flag utilization with the command:

SCP or ‘scp’ within the Terminal is simple to make use of. The essential command syntax is ‘scp’ adopted by file identify, person identify, server identify or IP tackle, and distant listing path on that server to entry. For instance:

tells scp to repeat an area file within the pwd named “instance.txt” to the server at IP tackle 10.10.0.1 on that server’s filesystem listing named “directoryName” because the person named “remote_user” with the distant file copy to be named “instance.txt” additionally.

Should you omit the distant file’s identify the identical identify because the supply file might be used. If you wish to change the distant file’s identify to one thing else, embrace a brand new file identify after the distant listing path on the finish of the command:

Additionally word that the person indicated should have permissions within the distant listing specified so as to copy the file.

An reverse instance – copying a file on the distant server to your Mac, appears related. For instance:

copies the file named “instance.txt” in listing “directoryName” on the distant server to your Mac’s Desktop.

It’s also possible to specify flags instantly after the scp portion utilizing the a minus signal adopted by the choice.

Two flags after “scp ” can be utilized to specify both model one two of the SSH protocol: -1′ or -2′. For instance:

forces use of model two of the protocol to repeat the file instance.txt within the pwd to the distant server at 10.10.0.1 into the listing named “directoryName” with a brand new file identify of “newExample.txt”.

You possibly can copy total directories through the use of the -r flag..

A number of different flags you need to use with scp to alter the way in which it behaves are:

1. -4 Use IPv4 addressing solely
2. -6 Use IPv6 addressing solely
3. -B Batch mode (suppresses extra requests for authentication)
4. -C Permits compression on the connection
5. -F Use an alternate ssh config file for connections
6. -i Specifies an alternate non-public key file to make use of for connections
7. -l (Restrict) – Units connection bandwidth restrict in kb/s
8. -O (Previous) – Power older SCP protocol as a substitute of newer SSH SFTP protocol throughout transfers
9. -o Go extra, non-command-line choices to ssh
10. -P Join on an alternate port quantity aside from 22
11. -p Protect all native file metadata on the distant file after copy, together with dates and occasions
12. -q (Quiet) – do not show file copy progress information in Terminal
13. -R (Distant) – Power using the distant model of scp for copies as a substitute of the native one
14. -r Recursively copy total directories as a substitute of simply single recordsdata
15. -S Use an alternate SSH program to handle the SSH connection
16. -v (Verbose) – Print additional information in Terminal for all scp operations

The -O possibility is supplied to be used in instances the place you might be connecting to older SSH servers which do not implement the newer SSH File Switch Protocol (additionally a part of SSH).

You need to use the -o choice to move extra parameters to ssh, which are not obtainable as command-line choices. See the scp man web page for extra particulars.

scp works completely high-quality in your native community between completely different sorts of computer systems and working methods. You possibly can hook up with and switch recordsdata between two LAN computer systems simply as simply as distant web computer systems, assuming each LAN computer systems are working SSH.

Microsoft inclues SSH in later releases of Home windows 10 starting in 2019. To be used with earlier variations of Home windows, you’ll have to put in a third-party SSH server on the Home windows pc.

Some fascinating books on SSH you could need to take a look at embrace:

In future articles we’ll discover transferring recordsdata in Terminal utilizing two extra fashionable networking protocols: SFTP and rsync.