SYSCTL(3)

🌈 SYSCTL(3) 🌈

okay bestie, welcome to SYSCTL(3) from the Library Functions Manual — this is the whole lore on getting or setting system information. 💅

✨ NAME ✨

sysctl, sysctlbyname, sysctlnametomib — get or set system information

📚 LIBRARY 📚

Standard C Library (libc, -lc)

🛠️ SYNOPSIS 🛠️

#include <sys/types.h>
#include <sys/sysctl.h>

int
sysctl(const int *name, u_int namelen, void *oldp, size_t *oldlenp,
    const void *newp, size_t newlen);

int
sysctlbyname(const char *name, void *oldp, size_t *oldlenp,
    const void *newp, size_t newlen);

int
sysctlnametomib(const char *name, int *mibp, size_t *sizep);

💖 DESCRIPTION 💖

So the sysctl() function retrieves system information and lets processes with appropriate privileges set system information. The info available from sysctl() consists of integers, strings, and tables. You can also retrieve and set this from the command interface using the sysctl(8) utility. ✨

Unless explicitly noted below, sysctl() returns a consistent snapshot of the data requested. Consistency is obtained by locking the destination buffer into memory so that the data may be copied out without blocking. Calls to sysctl() are serialized to avoid deadlock. 🔒

The state is described using a “Management Information Base” (MIB) style name, listed in name, which is a namelen length array of integers.

The sysctlbyname() function accepts an ASCII representation of the name and internally looks up the integer name vector. Apart from that, it behaves the same as the standard sysctl() function. 🦋

The information is copied into the buffer specified by oldp. The size of the buffer is given by the location specified by oldlenp before the call, and that location gives the amount of data copied after a successful call and after a call that returns with the error code ENOMEM. If the amount of data available is greater than the size of the buffer supplied, the call supplies as much data as fits in the buffer provided and returns with the error code ENOMEM. If the old value is not desired, oldp and oldlenp should be set to NULL. 😭

The size of the available data can be determined by calling sysctl() with the NULL argument for oldp. The size of the available data will be returned in the location pointed to by oldlenp. For some operations, the amount of space may change often. For these operations, the system attempts to round up so that the returned size is large enough for a call to return the data shortly thereafter. 🔥

To set a new value, newp is set to point to a buffer of length newlen from which the requested value is to be taken. If a new value is not to be set, newp should be set to NULL and newlen set to 0.

The sysctlnametomib() function accepts an ASCII representation of the name, looks up the integer name vector, and returns the numeric representation in the mib array pointed to by mibp. The number of elements in the mib array is given by the location specified by sizep before the call, and that location gives the number of entries copied after a successful call. The resulting mib and size may be used in subsequent sysctl() calls to get the data associated with the requested ASCII name. This interface is intended for use by applications that want to repeatedly request the same variable (the sysctl() function runs in about a third the time as the same request made via the sysctlbyname() function). The sysctlnametomib() function is also useful for fetching mib prefixes and then adding a final component. For example, to fetch process information for processes with pid's less than 100: 👑

int i, mib[4];
size_t len;
struct kinfo_proc kp;

/* Fill out the first three components of the mib */
len = 4;
sysctlnametomib("kern.proc.pid", mib, &len);

/* Fetch and print entries for pid's < 100 */
for (i = 0; i < 100; i++) {
        mib[3] = i;
        len = sizeof(kp);
        if (sysctl(mib, 4, &kp, &len, NULL, 0) == -1)
                perror("sysctl");
        else if (len > 0)
                printkproc(&kp);
}

The top level names are defined with a CTL_ prefix in <sys/sysctl.h>, and are as follows. The next and subsequent levels down are found in the include files listed here, and described in separate sections below. 🌸

• CTL_DEBUG — next level names: <sys/sysctl.h>; description: Debugging
• CTL_VFS — next level names: <sys/mount.h>; description: File system
• CTL_HW — next level names: <sys/sysctl.h>; description: Generic CPU, I/O
• CTL_KERN — next level names: <sys/sysctl.h>; description: High kernel limits
• CTL_MACHDEP — next level names: <sys/sysctl.h>; description: Machine dependent
• CTL_NET — next level names: <sys/socket.h>; description: Networking
• CTL_USER — next level names: <sys/sysctl.h>; description: User-level
• CTL_VM — next level names: <vm/vm_param.h>; description: Virtual memory

For example, the following retrieves the maximum number of processes allowed in the system: 💀

int mib[2], maxproc;
size_t len;

mib[0] = CTL_KERN;
mib[1] = KERN_MAXPROC;
len = sizeof(maxproc);
sysctl(mib, 2, &maxproc, &len, NULL, 0);

To retrieve the standard search path for the system utilities: 🎀

int mib[2];
size_t len;
char *p;

mib[0] = CTL_USER;
mib[1] = USER_CS_PATH;
sysctl(mib, 2, NULL, &len, NULL, 0);
p = malloc(len);
sysctl(mib, 2, p, &len, NULL, 0);

🧸 CTL_DEBUG 🧸

The debugging variables vary from system to system. A debugging variable may be added or deleted without need to recompile sysctl() to know about it. Each time it runs, sysctl() gets the list of debugging variables from the kernel and displays their current values. The system defines twenty (struct ctldebug) variables named debug0 through debug19. They are declared as separate variables so that they can be individually initialized at the location of their associated variable. The loader prevents multiple use of the same variable by issuing errors if a variable is initialized in more than one place. For example, to export the variable dospecialcheck as a debugging variable, the following declaration would be used: 🙈

int dospecialcheck = 1;
struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck };

🦋 CTL_VFS 🦋

A distinguished second level name, VFS_GENERIC, is used to get general information about all file systems. One of its third level identifiers is VFS_MAXTYPENUM that gives the highest valid file system type number. Its other third level identifier is VFS_CONF that returns configuration information about the file system type given as a fourth level identifier (see getvfsbyname(3) as an example of its use). The remaining second level identifiers are the file system type number returned by a statfs(2) call or from VFS_CONF. The third level identifiers available for each file system are given in the header file that defines the mount argument structure for that file system. 🌈

💻 CTL_HW 💻

The string and integer information available for the CTL_HW level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value. ✨

• HW_MACHINE — type: string; changeable: no. The machine class.
• HW_MODEL — type: string; changeable: no. The machine model
• HW_NCPU — type: integer; changeable: no. The number of cpus.
• HW_BYTEORDER — type: integer; changeable: no. The byteorder (4321 or 1234).
• HW_PHYSMEM — type: integer; changeable: no. Amount of physical memory (in bytes), minus the amount used by the kernel, pre-loaded modules, and (on x86) the dcons buffer.
• HW_USERMEM — type: integer; changeable: no. Amount of memory (in bytes) which is not wired.
• HW_PAGESIZE — type: integer; changeable: no. The software page size.
• HW_FLOATINGPT — type: integer; changeable: no. Nonzero if the floating point support is in hardware.
• HW_MACHINE_ARCH — type: string; changeable: no. The machine dependent architecture type.
• HW_REALMEM — type: integer; changeable: no. Amount of memory (in bytes) reported by the firmware. That value is sometimes not sane; in that case, the kernel reports the max memory address instead.
• HW_AVAILPAGES — type: integer; changeable: no. The same value as HW_PHYSMEM, measured in pages rather than bytes.

👑 CTL_KERN 👑

The string and integer information available for the CTL_KERN level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value. The types of data currently available are process information, system vnodes, the open file entries, routing table entries, virtual memory statistics, load average history, and clock rate information. 🫶

okay so picking the second-level name list right back up where it left off — here's the rest of the menu, with the type and whether you're allowed to change it 💅

• KERN_ARGMAX — integer — changeable: no 🙅
• KERN_BOOTFILE — string — changeable: yes ✨
• KERN_BOOTTIME — struct timeval — changeable: no
• KERN_CLOCKRATE — struct clockinfo — changeable: no
• KERN_FILE — struct xfile — changeable: no
• KERN_HOSTID — integer — changeable: yes
• KERN_HOSTUUID — string — changeable: yes
• KERN_HOSTNAME — string — changeable: yes
• KERN_JOB_CONTROL — integer — changeable: no
• KERN_MAXFILES — integer — changeable: yes
• KERN_MAXFILESPERPROC — integer — changeable: yes
• KERN_MAXPROC — integer — changeable: no
• KERN_MAXPROCPERUID — integer — changeable: yes
• KERN_MAXVNODES — integer — changeable: yes
• KERN_NGROUPS — integer — changeable: no
• KERN_NISDOMAINNAME — string — changeable: yes
• KERN_OSRELDATE — integer — changeable: no
• KERN_OSRELEASE — string — changeable: no
• KERN_OSREV — integer — changeable: no
• KERN_OSTYPE — string — changeable: no
• KERN_POSIX1 — integer — changeable: no
• KERN_PROC — node — changeable: not applicable
• KERN_PROF — node — changeable: not applicable
• KERN_QUANTUM — integer — changeable: yes
• KERN_SAVED_IDS — integer — changeable: no
• KERN_SECURELVL — integer — changeable: raise only 🚨
• KERN_UPDATEINTERVAL — integer — changeable: no
• KERN_VERSION — string — changeable: no
• KERN_VNODE — struct xvnode — changeable: no

---

and now the ✨lore✨ — what each of these little guys actually means:

• KERN_ARGMAX — the maximum bytes of argument to execve(2).
• KERN_BOOTFILE — the full pathname of the file the kernel got loaded from.
• KERN_BOOTTIME — you get a struct timeval structure back, and inside it is the time the system was booted. receipts for when the machine woke up 🦋
• KERN_CLOCKRATE — you get a struct clockinfo structure back. Inside: the clock, statistics clock and profiling clock frequencies, the number of micro-seconds per hz tick, and the skew rate.
• KERN_FILE — returns the entire file table. The data you get is an array of struct xfile, and its size depends on how many of those objects currently exist in the system.
• KERN_HOSTID — get or set the host ID.
• KERN_HOSTUUID — get or set the host's universally unique identifier (UUID). so official 👑
• KERN_HOSTNAME — get or set the hostname. yes bestie you can just set it.
• KERN_JOB_CONTROL — returns 1 if job control is available on this system, otherwise 0.
• KERN_MAXFILES — the maximum number of files that may be open in the system.
• KERN_MAXFILESPERPROC — the maximum number of files that may be open for a single process. heads up though: this limit only applies to processes with an effective uid of nonzero at the time of the open request. Files that have already been opened are not affected if the limit or the effective uid is changed. no take-backs, it's giving grandfather clause 💅
• KERN_MAXPROC — the maximum number of concurrent processes the system will allow.
• KERN_MAXPROCPERUID — the maximum number of concurrent processes the system will allow for a single effective uid. same energy as above: it only applies to processes with an effective uid of nonzero at the time of a fork request, and processes that have already been started are not affected if the limit is changed.
• KERN_MAXVNODES — the maximum number of vnodes available on the system.
• KERN_NGROUPS — the maximum number of supplemental groups.
• KERN_NISDOMAINNAME — the name of the current YP/NIS domain.
• KERN_OSRELDATE — the kernel release version, in the format MmmRxx, where M is the major version, mm is the two digit minor version, R is 0 if release branch, otherwise 1, and xx is updated when the available APIs change.

ngl this one's a whole decoder ring 🕵️ — the userland release version lives in <osreldate.h>; parse this file if you need to get the release version of the currently installed userland.

• KERN_OSRELEASE — the system release string.
• KERN_OSREV — the system revision string.
• KERN_OSTYPE — the system type string.
• KERN_POSIX1 — the version of IEEE Std 1003.1 (“POSIX.1”) with which the system attempts to comply. attempts, bestie. attempts. 😭
• KERN_PROC — returns selected information about specific running processes. ✨

for the following names you get an array of struct kinfo_proc structures back, whose size depends on the current number of such objects in the system:

• KERN_PROC_ALL — fourth level: None
• KERN_PROC_PID — a process ID
• KERN_PROC_PGRP — a process group
• KERN_PROC_TTY — a tty device
• KERN_PROC_UID — a user ID
• KERN_PROC_RUID — a real user ID

and if the third level name is KERN_PROC_ARGS, then the command line argument array comes back in a flattened form, i.e. zero-terminated arguments follow each other. the total size of the array is returned. it's also possible for a process to set its own process title this way. 🎀 if the third level name is KERN_PROC_PATHNAME, the path of the process' text file is stored. for KERN_PROC_PATHNAME, a process ID of -1 implies the current process.

• KERN_PROC_ARGS — a process ID
• KERN_PROC_PATHNAME — a process ID

• KERN_PROF — returns profiling information about the kernel.

if the kernel is not compiled for profiling, attempts to retrieve any of the KERN_PROF values will fail with ENOENT. 💀

the third level names for the string and integer profiling information are below, and the changeable column shows whether a process with appropriate privilege may change the value.

• GPROF_STATE — integer — changeable: yes
• GPROF_COUNT — u_short[] — changeable: yes
• GPROF_FROMS — u_short[] — changeable: yes
• GPROF_TOS — struct tostruct — changeable: yes
• GPROF_GMONPARAM — struct gmonparam — changeable: no

the variables are as follows:

• GPROF_STATE — returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling is running or stopped.
• GPROF_COUNT — array of statistical program counter counts.
• GPROF_FROMS — array indexed by program counter of call-from points.
• GPROF_TOS — array of struct tostruct describing destination of calls and their counts.
• GPROF_GMONPARAM — structure giving the sizes of the above arrays.

• KERN_QUANTUM — the maximum period of time, in microseconds, for which a process is allowed to run without being preempted if other processes are in the run queue. ⏳
• KERN_SAVED_IDS — returns 1 if saved set-group and saved set-user ID is available.
• KERN_SECURELVL — the system security level.

this level may be raised by processes with appropriate privilege. it may not be lowered. 🚨 one-way street, no U-turns, no cap.

• KERN_VERSION — the system version string.
• KERN_VNODE — returns the entire vnode table. note, the vnode table is not necessarily a consistent snapshot of the system. the data you get is an array whose size depends on the current number of such objects in the system, and each element of the array consists of a struct xvnode.

---

🌐 CTL_NET 🌐

the string and integer information available for the CTL_NET level is detailed below. the changeable column shows whether a process with appropriate privilege may change the value.

• PF_ROUTE — routing messages — changeable: no
• PF_INET — IPv4 values — changeable: yes
• PF_INET6 — IPv6 values — changeable: yes

🛣️ PF_ROUTE

return the entire routing table or a subset of it. the data comes back as a sequence of routing messages (see route(4) for the header file, format and meaning). the length of each message is contained in the message header.

• the third level name is a protocol number, which is currently always 0.
• the fourth level name is an address family, which may be set to 0 to select all address families.
• the fifth, sixth, and seventh level names are as follows:
  • NET_RT_FLAGS — sixth level: rtflags — seventh level: None
  • NET_RT_DUMP — sixth level: None — seventh level: None or fib number
  • NET_RT_IFLIST — sixth level: 0 or if_index — seventh level: None
  • NET_RT_IFMALIST — sixth level: 0 or if_index — seventh level: None
  • NET_RT_IFLISTL — sixth level: 0 or if_index — seventh level: None

the NET_RT_IFMALIST name returns information about multicast group memberships on all interfaces if 0 is specified, or for the interface specified by if_index. 🫶

the NET_RT_IFLISTL is like NET_RT_IFLIST, just returning message header structs with additional fields allowing the interface to be extended without breaking binary compatibility. the NET_RT_IFLISTL uses 'l' versions of the message header structures: struct if_msghdrl and struct ifa_msghdrl. binary compatibility stays unbroken, we love to see it ✨

🌈 PF_INET

get or set various global information about the IPv4 (Internet Protocol version 4). the third level name is the protocol. the fourth level name is the variable name. the currently defined protocols and names are:

• icmp — bmcastecho — integer — changeable: yes
• icmp — maskrepl — integer — changeable: yes
• ip — forwarding — integer — changeable: yes
• ip — redirect — integer — changeable: yes
• ip — ttl — integer — changeable: yes
• udp — checksum — integer — changeable: yes

the variables are as follows:

• icmp.bmcastecho — returns 1 if an ICMP echo request aimed at a broadcast or multicast address is supposed to get an answer back. 👀
• icmp.maskrepl — returns 1 if ICMP network mask requests are meant to be answered.
• ip.forwarding — returns 1 when IP forwarding is enabled for the host, meaning the host is out here acting as a router. main character behavior fr 🫶
• ip.redirect — returns 1 when ICMP redirects may be sent by the host. Heads up bestie: this one is ignored unless the host is routing IP packets, and it should normally be enabled on all systems.
• ip.ttl — the maximum time-to-live (hop count) value for an IP packet sourced by the system. This value applies to normal transport protocols, not to ICMP. no cap.
• udp.checksum — returns 1 when UDP checksums are being computed and checked.

Disabling UDP checksums is strongly discouraged. like bestie pls don't, I'm begging 😭

For variables net.inet.*.ipsec, please refer to ipsec(4). 💅

---

PF_INET6 🌈

Get or set various global information about the IPv6 (Internet Protocol version 6). The third level name is the protocol. The fourth level name is the variable name. same energy as above, just, y'know, v6 ✨

For variables net.inet6.* please refer to inet6(4). For variables net.inet6.*.ipsec6, please refer to ipsec(4).

---

CTL_USER 🎀

The string and integer information available for the CTL_USER level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value. (spoiler: literally none of these are changeable, they're all no — they're just out here vibing as read-only facts about your system 🧚)

• USER_BC_BASE_MAX — type integer, changeable: no
• USER_BC_DIM_MAX — type integer, changeable: no
• USER_BC_SCALE_MAX — type integer, changeable: no
• USER_BC_STRING_MAX — type integer, changeable: no
• USER_COLL_WEIGHTS_MAX — type integer, changeable: no
• USER_CS_PATH — type string, changeable: no
• USER_EXPR_NEST_MAX — type integer, changeable: no
• USER_LINE_MAX — type integer, changeable: no
• USER_POSIX2_CHAR_TERM — type integer, changeable: no
• USER_POSIX2_C_BIND — type integer, changeable: no
• USER_POSIX2_C_DEV — type integer, changeable: no
• USER_POSIX2_FORT_DEV — type integer, changeable: no
• USER_POSIX2_FORT_RUN — type integer, changeable: no
• USER_POSIX2_LOCALEDEF — type integer, changeable: no
• USER_POSIX2_SW_DEV — type integer, changeable: no
• USER_POSIX2_UPE — type integer, changeable: no
• USER_POSIX2_VERSION — type integer, changeable: no
• USER_RE_DUP_MAX — type integer, changeable: no
• USER_STREAM_MAX — type integer, changeable: no
• USER_TZNAME_MAX — type integer, changeable: no

Okay now the actual gossip on each one 👇

• USER_BC_BASE_MAX — the maximum ibase/obase values in the bc(1) utility.
• USER_BC_DIM_MAX — the maximum array size in the bc(1) utility.
• USER_BC_SCALE_MAX — the maximum scale value in the bc(1) utility.
• USER_BC_STRING_MAX — the maximum string length in the bc(1) utility.
• USER_COLL_WEIGHTS_MAX — the maximum number of weights that can be assigned to any entry of the LC_COLLATE order keyword in the locale definition file.
• USER_CS_PATH — return a value for the PATH environment variable that finds all the standard utilities. she's helpful like that 💅
• USER_EXPR_NEST_MAX — the maximum number of expressions that can be nested within parenthesis by the expr(1) utility.
• USER_LINE_MAX — the maximum length in bytes of a text-processing utility's input line.
• USER_POSIX2_CHAR_TERM — return 1 if the system supports at least one terminal type capable of all operations described in IEEE Std 1003.2 (“POSIX.2”), otherwise 0.
• USER_POSIX2_C_BIND — return 1 if the system's C-language development facilities support the C-Language Bindings Option, otherwise 0.
• USER_POSIX2_C_DEV — return 1 if the system supports the C-Language Development Utilities Option, otherwise 0.
• USER_POSIX2_FORT_DEV — return 1 if the system supports the FORTRAN Development Utilities Option, otherwise 0.
• USER_POSIX2_FORT_RUN — return 1 if the system supports the FORTRAN Runtime Utilities Option, otherwise 0.
• USER_POSIX2_LOCALEDEF — return 1 if the system supports the creation of locales, otherwise 0.
• USER_POSIX2_SW_DEV — return 1 if the system supports the Software Development Utilities Option, otherwise 0.
• USER_POSIX2_UPE — return 1 if the system supports the User Portability Utilities Option, otherwise 0.
• USER_POSIX2_VERSION — the version of IEEE Std 1003.2 (“POSIX.2”) with which the system attempts to comply.
• USER_RE_DUP_MAX — the maximum number of repeated occurrences of a regular expression permitted when using interval notation. regex girlies rise 🦋
• USER_STREAM_MAX — the minimum maximum number of streams that a process may have open at any one time.
• USER_TZNAME_MAX — the minimum maximum number of types supported for the name of a timezone.

---

CTL_VM 💀

The string and integer information available for the CTL_VM level is detailed below. The changeable column shows whether a process with appropriate privilege may change the value. and bestie, notice the maybe in there — she's mysterious, she's complicated, we love her 🎀

• VM_LOADAVG — type struct loadavg, changeable: no
• VM_TOTAL — type struct vmtotal, changeable: no
• VM_SWAPPING_ENABLED — type integer, changeable: maybe
• VM_V_FREE_MIN — type integer, changeable: yes
• VM_V_FREE_RESERVED — type integer, changeable: yes
• VM_V_FREE_TARGET — type integer, changeable: yes
• VM_V_INACTIVE_TARGET — type integer, changeable: yes
• VM_V_PAGEOUT_FREE_MIN — type integer, changeable: yes
• VM_OVERCOMMIT — type integer, changeable: yes

And the lore on each 🫶

• VM_LOADAVG — return the load average history. The returned data consists of a struct loadavg.
• VM_TOTAL — return the system wide virtual memory statistics. The returned data consists of a struct vmtotal.
• VM_SWAPPING_ENABLED — 1 if process swapping is enabled or 0 if disabled. Important: this variable is permanently set to 0 if the kernel was built with swapping disabled. like, no take-backs, it's just 0 forever, that's the law 😤
• VM_V_FREE_MIN — minimum amount of memory (cache memory plus free memory) required to be available before a process waiting on memory will be awakened.
• VM_V_FREE_RESERVED — processes will awaken the pageout daemon and wait for memory if the number of free and cached pages drops below this value.
• VM_V_FREE_TARGET — the total amount of free memory (including cache memory) that the pageout daemon tries to maintain.
• VM_V_INACTIVE_TARGET — the desired number of inactive pages that the pageout daemon should achieve when it runs. Inactive pages can be quickly inserted into process address space when needed. she's on standby, ready to be called up 💅
• VM_V_PAGEOUT_FREE_MIN — if the amount of free and cache memory falls below this value, the pageout daemon will enter "memory conserving mode" to avoid deadlock.
• VM_OVERCOMMIT — overcommit behaviour, as described in tuning(7).

---

RETURN VALUES ✨

Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error. zero means slay, negative one means go read errno bestie 😭

---

FILES 📁

• <sys/sysctl.h> — definitions for top level identifiers, second level kernel and hardware identifiers, and user level identifiers
• <sys/socket.h> — definitions for second level network identifiers
• <sys/gmon.h> — definitions for third level profiling identifiers
• <vm/vm_param.h> — definitions for second level virtual memory identifiers
• <netinet/in.h> — definitions for third level IPv4/IPv6 identifiers and fourth level IPv4/v6 identifiers
• <netinet/icmp_var.h> — definitions for fourth level ICMP identifiers
• <netinet/icmp6.h> — definitions for fourth level ICMPv6 identifiers
• <netinet/udp_var.h> — definitions for fourth level UDP identifiers

---

ERRORS 😵

The following errors may be reported:

• [EFAULT] — the buffer name, oldp, newp, or length pointer oldlenp contains an invalid address.
• [EINVAL] — the name array is less than two or greater than CTL_MAXNAME.
• [EINVAL] — a non-null newp is given and its specified length in newlen is too large or too small.
• [ENOMEM] — the length pointed to by oldlenp is too short to hold the requested value.
• [ENOMEM] — the smaller of either the length pointed to by oldlenp or the estimated size of the returned data exceeds the system limit on locked memory.
• [ENOMEM] — locking the buffer oldp, or a portion of the buffer if the estimated size of the data to be returned is smaller, would cause the process to exceed its per-process locked memory limit.
• [ENOTDIR] — the name array specifies an intermediate rather than terminal name.
• [EISDIR] — the name array specifies a terminal name, but the actual name is not terminal.
• [ENOENT] — the name array specifies a value that is unknown.
• [EPERM] — an attempt is made to set a read-only value. girl it said read-only, hands off 🙈
• [EPERM] — a process without appropriate privilege attempts to set a value.

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SEE ALSO 👑

confstr(3), kvm(3), sysconf(3), sysctl(8)

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HISTORY 🌸

The sysctl() function first appeared in 4.4BSD.

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okay that's the whole page bestie, you're officially a sysctl(3) girlie now 💖 this one's from the Debian crew, dated March 22, 2019, and it's filed under SYSCTL(3) — go forth and read your kernel's mind, mwah 🫶✨