STRUCT CTL_TABLE_HEADER(9)

🦋 NAME 🦋

okay bestie, this is the struct ctl_table_header(9) page from the Kernel API Manual — and it's all about struct ctl_table_header, the struct that maintains dynamic lists of struct ctl_table trees. slay 💅

✨ SYNOPSIS ✨

here's the whole struct, copied exactly so you can vibe-check the shape:

       struct ctl_table_header {
           union {
             struct {
               const struct ctl_table *ctl_table;
               int ctl_table_size;
               int used;
               int count;
               int nreg;
             };
             struct rcu_head rcu;
           };
           struct completion *unregistering;
           const struct ctl_table *ctl_table_arg;
           struct ctl_table_root *root;
           struct ctl_table_set *set;
           struct ctl_dir *parent;
           struct ctl_node *node;
           struct hlist_head inodes;
           enum {
             SYSCTL_TABLE_TYPE_DEFAULT,
             SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY,
           } type;
        };

🎀 Members 🎀

member-by-member, no skips, periodt 💅

• {unnamed_union} — anonymous.
• {unnamed_struct} — anonymous.
• ctl_table — pointer to the first element in the ctl_table array.
• ctl_table_size — number of elements pointed by ctl_table.
• used — The entry will never be touched when it's equal to 0.
• count — upped every time something is added to inodes, and downed every time something is removed from inodes.
• nreg — when nreg drops to 0, the ctl_table_header will be unregistered.
• rcu — delays the freeing of the inode. Introduced with "unfuck proc_sysctl ->d_compare" — that's the note, fr fr.
• type — enumeration to differentiate between ctl target types:
  • type.SYSCTL_TABLE_TYPE_DEFAULT — ctl target with no special considerations.
  • type.SYSCTL_TABLE_TYPE_PERMANENTLY_EMPTY — Identifies a permanently empty dir target to serve as a mount point.

🌈 SEE ALSO 🌈

• Kernel file ./include/linux/sysctl.h — go peek, bestie. iykyk ✨

💌 that's the whole page, bestie — source/version ./include/linux, dated October 2026, signing off! 💖