The UNIX system has been in wide use for over 20 years, and has helped to define many areas of computing.
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so unserious!!! "splice() is zero-copy hohoho" i literally don't even care it just lets me express my intent to the kernel so it can optimize better this is so obvious ugh
There are different kinds of sockets that support various communication semantics, such as reliable delivery of data, preservation of message ordering, and preservation of
message boundaries.
i think if linux is allowed to make a broken cryptography socket i should be allowed to make an actually working file handle with specified buffering semantics
ok the reason i opened this damn book at all is because i wanted to see if they described the absurd posix requirement to globally share file buffers as mutable memory mappings
A file is a linear array of bytes with at least one name. A file exists until all its names are deleted explicitly and no process holds a descriptor for it.
nope
A process acquires a descriptor for a file by opening that file's name with the open system call. I/O devices are accessed as files.
nope
FIFOs are implemented in 4.4BSD only because they are required by the standard.
guy who spends a whole paragraph hyping up a feature and then blames the "standard"
The socket mechanism requires extensions to the traditional UNIX I/O system calls to provide the associated naming and connection semantics.
i'm 100000% gonna claim sockets as inspo
the filesystem section now. no mention of read() and write() being immediately globally visible
Within their home directories, users can create directories as easily as they can regular files. Thus, a user can build arbitrarily complex subhierarchies.
they lean on the user and perms system here but you can't really build a subhierarchy safely without interference because everything is always globally visible lmao
A three-level access-control mechanism is provided for the protection of files.
pathetic
there is half a page on how path length limitations lead to breakage
the long filenames first introduced in 4.2BSD practically eliminate it.
PATH_MAX still exists
The kernel provides many ancillary services, such as buffer management, message routing, standardized interfaces to the protocols, and interfaces to the network interface drivers
for the use of the various network protocols.
network gets all the toys. buffer management????
The CSRG chose TCP/IP as the first network to incorporate into the socket IPC framework, because a 4.1 BSD-based implementation was publicly available from a DARPA-sponsored project at Bolt, Beranek, and Newman (BBN).
a terrible day in history
god i'm so mad networking gets to describe routing protocols but i can't route my own i/o to my own disk????
The kernel can be logically divided into a top half and a bottom half
Processes cooperate in the sharing of system resources, such as the CPU.
well they don't really cooperate. they're forced to work
The top and bottom halves of the kernel also work together in implementing certain system operations, such as I/O.
sure. valid ✅
Typically, the top half will start an I/O operation, then relinquish the processor; then the requesting process will sleep, awaiting notification from the bottom half that the I/O request has completed.
there is nothing else that can be done
System performance requires that the kernel minimize the overhead in fielding and dispatching a system call.
unimaginative
