prctl

Section: System Calls (2)
Updated: 2026-02-08
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NAME

prctl - operations on a process or thread  

LIBRARY

Standard C library (libc,~-lc)  

SYNOPSIS

#include <linux/prctl.h>  /* Definition of PR_* constants */
#include <sys/prctl.h>
int prctl(int op, ...);

 

DESCRIPTION

prctl() manipulates various aspects of the behavior of the calling thread or process. prctl() is called with a first argument describing what to do, and further arguments with a significance depending on the first one. The first argument can be:

PR_CAP_AMBIENT

PR_CAPBSET_READ PR_CAPBSET_DROP PR_SET_CHILD_SUBREAPER PR_GET_CHILD_SUBREAPER PR_SET_DUMPABLE PR_GET_DUMPABLE PR_SET_ENDIAN PR_GET_ENDIAN PR_SET_FP_MODE PR_GET_FP_MODE PR_SET_FPEMU PR_GET_FPEMU PR_SET_FPEXC PR_GET_FPEXC PR_SET_IO_FLUSHER PR_GET_IO_FLUSHER PR_SET_KEEPCAPS PR_GET_KEEPCAPS PR_MCE_KILL PR_MCE_KILL_GET PR_SET_MM PR_SET_VMA PR_MPX_ENABLE_MANAGEMENT PR_MPX_DISABLE_MANAGEMENT PR_SET_NAME PR_GET_NAME PR_SET_NO_NEW_PRIVS PR_GET_NO_NEW_PRIVS PR_PAC_RESET_KEYS PR_SET_PDEATHSIG PR_GET_PDEATHSIG PR_SET_PTRACER PR_SET_SECCOMP PR_GET_SECCOMP PR_SET_SECUREBITS PR_GET_SECUREBITS PR_GET_SPECULATION_CTRL PR_SET_SPECULATION_CTRL PR_SVE_SET_VL PR_SVE_GET_VL PR_SET_SYSCALL_USER_DISPATCH PR_SET_TAGGED_ADDR_CTRL PR_GET_TAGGED_ADDR_CTRL PR_TASK_PERF_EVENTS_DISABLE PR_TASK_PERF_EVENTS_ENABLE PR_SET_THP_DISABLE PR_GET_THP_DISABLE PR_GET_TID_ADDRESS PR_SET_TIMERSLACK PR_GET_TIMERSLACK PR_SET_TIMING PR_GET_TIMING PR_SET_TSC PR_GET_TSC PR_SET_UNALIGN PR_GET_UNALIGN PR_GET_AUXV PR_SET_MDWE PR_GET_MDWE PR_RISCV_SET_ICACHE_FLUSH_CTX PR_FUTEX_HASH

 

RETURN VALUE

On success, a nonnegative value is returned. On error, -1 is returned, and errno is set to indicate the error.  

ERRORS

EINVAL

The value of op is not recognized, or not supported on this system.

EINVAL

An unused argument is nonzero.

 

VERSIONS

IRIX has a prctl() system call (also introduced in Linux 2.1.44 as irix_prctl on the MIPS architecture), with prototype ptrdiff_t prctl(int op, int arg2, int arg3); and operations to get the maximum number of processes per user, get the maximum number of processors the calling process can use, find out whether a specified process is currently blocked, get or set the maximum stack size, and so on.  

STANDARDS

Linux.  

HISTORY

Linux 2.1.57, glibc 2.0.6  

CAVEATS

The prototype of the libc wrapper uses a variadic argument list. This makes it necessary to pass the arguments with the right width. When passing numeric constants, such as 0, use a suffix: 0L. Careless use of some prctl() operations can confuse the user-space run-time environment, so these operations should be used with care.  

SEE ALSO

signal(2), PR_CAP_AMBIENT(2const), PR_CAPBSET_READ(2const), PR_CAPBSET_DROP(2const), PR_SET_CHILD_SUBREAPER(2const), PR_GET_CHILD_SUBREAPER(2const), PR_SET_DUMPABLE(2const), PR_GET_DUMPABLE(2const), PR_SET_ENDIAN(2const), PR_GET_ENDIAN(2const), PR_SET_FP_MODE(2const), PR_GET_FP_MODE(2const), PR_SET_FPEMU(2const), PR_GET_FPEMU(2const), PR_SET_FPEXC(2const), PR_GET_FPEXC(2const), PR_SET_IO_FLUSHER(2const), PR_GET_IO_FLUSHER(2const), PR_SET_KEEPCAPS(2const), PR_GET_KEEPCAPS(2const), PR_MCE_KILL(2const), PR_MCE_KILL_GET(2const), PR_SET_MM(2const), PR_SET_VMA(2const), PR_MPX_ENABLE_MANAGEMENT(2const), PR_MPX_DISABLE_MANAGEMENT(2const), PR_SET_NAME(2const), PR_GET_NAME(2const), PR_SET_NO_NEW_PRIVS(2const), PR_GET_NO_NEW_PRIVS(2const), PR_PAC_RESET_KEYS(2const), PR_SET_PDEATHSIG(2const), PR_GET_PDEATHSIG(2const), PR_SET_PTRACER(2const), PR_SET_SECCOMP(2const), PR_GET_SECCOMP(2const), PR_SET_SECUREBITS(2const), PR_GET_SECUREBITS(2const), PR_SET_SPECULATION_CTRL(2const), PR_GET_SPECULATION_CTRL(2const), PR_SVE_SET_VL(2const), PR_SVE_GET_VL(2const), PR_SET_SYSCALL_USER_DISPATCH(2const), PR_SET_TAGGED_ADDR_CTRL(2const), PR_GET_TAGGED_ADDR_CTRL(2const), PR_TASK_PERF_EVENTS_DISABLE(2const), PR_TASK_PERF_EVENTS_ENABLE(2const), PR_SET_THP_DISABLE(2const), PR_GET_THP_DISABLE(2const), PR_GET_TID_ADDRESS(2const), PR_SET_TIMERSLACK(2const), PR_GET_TIMERSLACK(2const), PR_SET_TIMING(2const), PR_GET_TIMING(2const), PR_SET_TSC(2const), PR_GET_TSC(2const), PR_SET_UNALIGN(2const), PR_GET_UNALIGN(2const), PR_GET_AUXV(2const), PR_SET_MDWE(2const), PR_GET_MDWE(2const), PR_RISCV_SET_ICACHE_FLUSH_CTX(2const), PR_FUTEX_HASH(2const), core(5)

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Index

NAME

LIBRARY

SYNOPSIS

DESCRIPTION

RETURN VALUE

ERRORS

VERSIONS

STANDARDS

HISTORY

CAVEATS

SEE ALSO