EC
ulimit
BashERRORCriticalScriptingHIGH confidence

Resource limit exceeded

Production Risk

Common in high-concurrency services; set ulimits in service configuration, not just the interactive shell.

What this means

When a process exceeds a resource limit set by ulimit, the kernel either sends a signal (SIGXCPU, SIGXFSZ, SIGSEGV for stack overflow) or returns ENOMEM/EFBIG to the offending syscall. Scripts fail with the exit code of the killed or erroring process.

Why it happens
  1. 1ulimit -n (open files) exceeded — too many open file descriptors
  2. 2ulimit -v (virtual memory) exceeded — process uses too much memory
  3. 3ulimit -s (stack size) exceeded — deep recursion or large stack allocations
  4. 4ulimit -u (processes) exceeded — cannot fork new processes
How to reproduce

Script opens too many files, hitting the ulimit -n limit.

trigger — this will error
trigger — this will error
#!/bin/bash
# Check current limits
ulimit -n  # open files limit (commonly 1024)

# Hit the file descriptor limit
for i in $(seq 1 2000); do
  exec {fd}<>/tmp/testfile$i
done

expected output

bash: /tmp/testfile1025: too many open files
Exit: 1

Fix 1

Increase the file descriptor limit

WHEN A service opens many files or connections

Increase the file descriptor limit
# In the script or service unit file:
ulimit -n 65536

# Permanently via /etc/security/limits.conf:
# myuser soft nofile 65536
# myuser hard nofile 65536

# For systemd services:
# [Service]
# LimitNOFILE=65536

Why this works

Increasing the fd limit allows more simultaneous open files; set via ulimit, limits.conf, or systemd LimitNOFILE.

Fix 2

Close file descriptors when done

WHEN Script accumulates open fds in a loop

Close file descriptors when done
#!/bin/bash
for file in /data/*.log; do
  process_file "$file"
  # Ensure any fds opened in process_file are closed
  # (use subshells to auto-close fds)
done

Why this works

Fds are a finite resource; always close them explicitly rather than relying on process exit.

Sources

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