Questions tagged [c]
C is a general-purpose computer programming language used for operating systems, games and other high performance work and is clearly distinct from C++. It was developed in 1972 by Dennis Ritchie for use with the Unix operating system.
869 questions
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Why does there appear to be a discrepancy when trying to programmatically access files associated with different tasks in Linux from kernel space?
As a way to better understand Linux kernel structures, interacting with and pulling information from these (and also getting more experience coding in C), I've been building simple kernel modules to ...
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How many environments are stored in the stack? [duplicate]
When I used the getenv() function to get the address of USER, I got 0x7ffceae5e923 but when randomly checking the address using gdb, the $USER variable was stored at 0x7ffffffffe90e [ I started a ...
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Why PAM modules are restricted from accessing keys on root keyring?
I'm writing a special PAM module that is supposed to authenticate user with a password stored in kernel keyring. The key is added by running the following command as root: keyctl add user some-key 123 ...
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How does printf() actually work? [duplicate]
When I execute the c file #include <stdio.h> #include <stdlib.h> int main(){ printf("before the system call. I am too excited!\n"); system("ps"); ...
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how does Visual Studio Code resolve includes & macros for autocomplete & build?
If using only the C/++ Extension from Microsoft in Visual Studio Code, then how does preprocessing of includes & macros for autocomplete work? Many include headers (such as sys/statvfs.h), depend ...
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Wrong attributes bitmask in READDIR requests on NFSv4.1
I'm struggling the following problem. I have an NFS v4.1 mount, where I have a directory with a couple of thousands files. I'm trying to list their names and types. Even with a minimal example program ...
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Changing all strcpy to strscpy
I am learning about Linux kernel development. I have cloned into the stable branch of Linux. I watched a tutorial from Greg KH on youtube that explains you can use the checkpatch.pl script to find ...
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Does a systemd service send org.freedesktop.DBus.Properties.PropertiesChanged signal at boot-up?
I have 2 systemd services. a.service b.service b depends on a but I don't want to explicitly mention the dependency in b.service file. Instead I am waiting on the org.freedesktop.DBus.Properties....
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Use libnm or popen(nmcli) to configure network programmatically?
We have a system where we need the user to be able to permanently change the network settings from the interface (via our C code), that used to be achieved by generating a new dhcpcd.conf file and ...
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Hit noise when playing part of wave file with ALSA PCM interface
I am working a WAVE file playing with ALSA PCM interface in Linux, and I heard noise when I played the file quickly and partially. Here is my playing function. static int playback_function(uint8_t *...
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Cannot see "file,line,func" fields in the journal
I am trying to use sd_journal_print_with_location() function. #include <systemd/sd-journal.h> int main() { sd_journal_print_with_location(LOG_INFO, "CODE_FILE=tst_file.c", "...
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Automatic flush of stream when reading input
I read in Advanced Programming in Unix Environment this: Line buffering comes with two caveats. First, the size of the buffer that the standard I/O library uses to collect each line is fixed, so I/O ...
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Send UDP data from one NIC and receive on another NIC on same machine
I have multiple NIC's on my Ubuntu machine. $ ifconfig docker0: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500 inet 172.17.0.1 netmask 255.255.0.0 broadcast 172.17.255.255 inet6 ...
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Get output into journal in a C written service
I have a small service written in C on Debian. This service automatically starts with Linux and does some file operations and other things as expected. The service prints some informational messages ...
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There is no file linux/init.h
I'm trying to write my own pci-device driver on an Ubuntu system. The example I found says that I need: #include <linux/init.h> #include <linux/module.h> #include <linux/pci.h> I'm ...
