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Jul
24
comment why doesn't strace use test syscalls to find out their indices in the system call table?
About the syscall numbers being fixed, this is simply the Linux stability policy. On systems without such a policy, you would not have any backwards compatibility and any binaries making use of syscall numbers (this means any static binaries, and also dynamic binaries that use the syscall() function) would be tied to the specific kernel version they were built for. You can find the Linux stability policy somewhere in the kernel documentation, but it shouldn't even need to be stated; this is just the most basic common sense about compatibility.
Jul
24
comment why doesn't strace use test syscalls to find out their indices in the system call table?
Man pages are not normative. They are meant to be descriptive, but sometimes the descriptions are not entirely correct. If you feel this text is misleading please submit a bug report to the Linux man pages project.
Jul
24
comment why doesn't strace use test syscalls to find out their indices in the system call table?
If you think the definitions of system call numbers could change from rebooting, you have some serious misunderstandings that might explain why you're asking this question to begin with. They are an absolute permanent fixed part of the public kernel API/ABI. For them not to be, binaries built for one kernel could not be used on another one.
Jul
24
comment why doesn't strace use test syscalls to find out their indices in the system call table?
How do you know open(foobar.txt, O_RDONLY) results in exactly one syscall and that's SYS_open? It might use SYS_openat. It might result in other system calls taking place as part of lazy binding in the dynamic linker, if this is the first call to open. Or it might involve other system calls internally for some other purpose. There is no trivial one-to-one mapping you can assume between library calls and system calls.
Jul
24
comment why doesn't strace use test syscalls to find out their indices in the system call table?
Also "first run after reboot" is a concept that doesn't make sense at all. How would it even know such a thing?
Jul
24
comment why doesn't strace use test syscalls to find out their indices in the system call table?
How would it make these test system calls except by using the constants from the system/kernel headers?
Jul
3
comment There is a delay when I press the letters
What an awful "feature"...
Jun
26
comment On OS X, why does sudo ls show hidden (dot) files?
From the POSIX Rationale, "Some historical implementations of the ls utility show all entries in a directory except dot and dot-dot when a superuser invokes ls without specifying the -a option. When "normal" users invoke ls without specifying -a, they should not see information about any files with names beginning with a <period> unless they were named as file operands." pubs.opengroup.org/onlinepubs/9699919799/utilities/ls.html
Jun
13
awarded  Student
May
27
comment How to write a script that accepts input from a file or from stdin?
@Suzana_K: I just tested with bash 4.3.33 and it works fine. I suspect you have a typo somewhere in the script or else some weird configuration getting processed. Are you entering the command interactively or in a script you're executing? Perhaps you could pastebin the script if you'd like me to look at it (or better yet, post a question here about why it's not working despite that it should).
May
27
comment How to write a script that accepts input from a file or from stdin?
@Suzana_K: What shell are you using? If that's true it's not a working implementation of the POSIX sh command/Bourne shell.
May
27
comment How to write a script that accepts input from a file or from stdin?
@Suzana_K: Not when it has no arguments, like here. In that case it just replaces file descriptors for the shell itself rather than a child process.
Apr
6
awarded  Famous Question
Dec
3
comment Preventing javascript from grabbing arrow keys
It seems to work, but only when activated explicitly. Is there any way to have it always active on certain sites?
Dec
3
comment Preventing javascript from grabbing arrow keys
Looks promising. I'm trying it.
Nov
5
comment Preventing javascript from grabbing arrow keys
I'm not familiar with the exact mechanism by which JS steals key events, but the goal would be to prevent overriding of at least the arrow keys, with the ability to use a blacklist or whitelist approach for allowing some sites to steal them. My impression is that the ability to bind keys when a particular object (like an edit area) is focused is important, so if it's possible to allow that while forbidding it at the whole-page scope, that would greatly lessen the need for whitelisting.
Nov
5
asked Preventing javascript from grabbing arrow keys
Sep
26
comment How do I patch the shellshock vulnerability on an obsolete Ubuntu system that I can't upgrade?
A closer analogy would be telling someone experiencing a bug in GCC to try clang. Both implement the same language (with different but sometimes overlapping sets of nonstandard extensions) and it's unlikely that the actual need is for "bash" but rather for "shell interpreter".
Sep
26
answered How do I patch the shellshock vulnerability on an obsolete Ubuntu system that I can't upgrade?
Jul
23
comment Are computers with more RAM potentially faster if not all memory is usually in use?
Part of the difficulty of this question is that "in use" is difficult to define for any modern operating system with virtual memory and memory-mapped files. For example, is the code ("text") segment of an executing program "used" or "cache"?