Open File Limits

Slug

JNBPBAMH7W6E

Fetches

0

Size

1775 B · 74 lines

Expires

never

Last fetch

—

Created

2026-09-07 00:36:01.580

Description

ulimit -n versus the process hard limit

#!/usr/bin/env bash
# Open file limits
# Read-only: compares ulimit -n with /proc/self/limits. Warns if the soft limit is under 1024.
# Exit 0 if healthy, 1 if the soft limit is low, 2 if it is under 256 or unreadable.
# Hosted on Runny.sh. Review the script page before you run it.

set -u

status=0
note() { printf '%s\n' "$*"; }
bump() {
  case $1 in
    crit) status=2 ;;
    warn) [ "$status" -lt 1 ] && status=1 ;;
  esac
}

note "=== Open file limits ==="
note "Host:     $(hostname 2>/dev/null || printf unknown)"
note "Pid:      $$"

soft=$(ulimit -n 2>/dev/null || true)
note "ulimit -n:${soft:-unknown}"

proc_soft=""
proc_hard=""
if [ -r /proc/self/limits ]; then
  note ""
  awk '/^Max open files|^Limit/ {print "  " $0}' /proc/self/limits
  proc_soft=$(awk '/^Max open files/ {print $4}' /proc/self/limits)
  proc_hard=$(awk '/^Max open files/ {print $5}' /proc/self/limits)
  note "Proc soft:${proc_soft:-unknown}"
  note "Proc hard:${proc_hard:-unknown}"
else
  note "/proc/self/limits is not readable"
  bump warn
fi

limit=${soft}
if [ -z "${limit}" ] || [ "${limit}" = "unlimited" ]; then
  limit=${proc_soft:-unlimited}
fi

note ""
case "$limit" in
  ''|*[!0-9]*)
    if [ "$limit" = "unlimited" ]; then
      note "          OK"
    else
      note "          WARNING: could not parse a numeric soft limit"
      bump warn
    fi
    ;;
  *)
    if [ "$limit" -lt 256 ]; then
      note "          CRITICAL: soft nofile is under 256"
      bump crit
    elif [ "$limit" -lt 1024 ]; then
      note "          WARNING: soft nofile is under 1024"
      bump warn
    else
      note "          OK"
    fi
    ;;
esac
note ""

case $status in
  0) note "Result: HEALTHY" ;;
  1) note "Result: WARNING" ;;
  *) note "Result: CRITICAL" ;;
esac
exit "$status"