Eduardo Bustamante's website

HTTP load testing with curl

Sun, 15 Feb 2015 00:00:00 -0800

It’s easy to use the curl command to load test a website. We’ll (ab)use the -K/--config option, to pass a configuration file like this:

silent = 1
output = "/dev/null"
write-out = "%{http_code} %{time_total}\n"
url = "http://dualbus.me/{,}{,}{,}{,,,,}{,,,,}{,,,,}"

The interesting part is the url. We’re requesting the same URL 1,000 times. (2x2x2x5x5x5). An easy way to compute that string:

dualbus@hp ~ % factor 1000
1000: 2 2 2 5 5 5

Now, you can use GNU xargs to do some requests in parallel (assuming you placed the configuration in config.txt):

printf '%.0sconfig.txt\n' {1..20} | xargs -P 20 -n 1 curl -K

Enjoy.

Updates

Feb 15, 2015: This answer from Ian Purton shows a different way of doing it (with ranges instead of alternations), so you can do: curl 'http://domain.name/#[1-100]'.

List of interesting commands

Tue, 02 Dec 2014 00:00:00 -0800

SSH Keys

rsa keys with openssl

# Write the public part of a RSA key in OpenSSH format (basically
# just prefix it with 'ssh-rsa' and collapse everything. Also remove
# the ASCII guards.
openssl pkey -in file.pem -pubout | sed -ne :a -e '1d;$!{H;n;ba;}' \
  -e 'x;s/\n//g;s/^/ssh-rsa /p'

# Generate a RSA private SSH key, using OpenSSL's genpkey command
# (4096 bits)
openssl genpkey -out file.pem -outform PEM -algorithm rsa \
  -pkeyopt rsa_keygen_bits:4096

Bash

group files by extension with associative arrays

# Read a list of files with sizes and group them by extension, adding
# the size.
  
declare -A files=();
while read -r size filename; do
  basename=${filename##*/}; ((files["${basename##*.}"]+=size));
done <<<  $'10 foo/bar/baz.ext\n20 foo/bar/bleh.ext\n40 music/some/song.mp3'
declare -p files
  
Output:
> declare -A files='([mp3]="40" [ext]="30" )'

Git

branches

# Delete a branch in a remote
git push <remote> :branch_name

# Update a remote, considering also deleted branches
git remote update -p # -p comes from 'prune'

GNU Bash bugs

Sun, 09 Mar 2014 00:00:00 -0800

This is a list of the bugs in GNU Bash that I’ve reported:

Improper array name validation for the ‘mapfile’ builtin
Segmentation fault when running recursive traps
Issue when using job control and SIGCHLD with bash 4.3 (trap is not being run)
Bash does not follow POSIX when return is called during the action of a trap
Executing ‘return’ inside RETURN trap causes function to recurse infinitely

f(){ trap return RETURN; }; f
Parent shell gets stopped when a child shell is created with job control but not interactive (bash -mc)

bash -s <<< 'for i in . .; do (bash -mc ": & wait") ; done'

Invalid byte sequence under UTF-8 locale generates a segmentation fault when using printf %q (ansic_quote)

$ cat command-name 
payload=$'\065\247\100\063\231\053\306\123\070\237\242\352\263'
"$payload"
  
$ cat printf-q 
payload=$'\065\247\100\063\231\053\306\123\070\237\242\352\263'
printf %q "$payload"
  
$ cat set-x 
payload=$'\065\247\100\063\231\053\306\123\070\237\242\352\263'
(set -x; : "$payload")

DEL character treated specially when preceded by a backslash when used in the RHS of the regex operator ([[ $'\177' =~ $'\\\177' ]])

for c in $'\001' $'\a' $'\177' $'\377'; do
    for r in "$c" "\\$c" "\\[$c]"; do
        [[ $c =~ $r ]];
        printf '[[ %q =~ %q ]] -> %d\n' "$c" "$r" "$?";
    done; printf %s\\n ---;
done;

Unexpected behavior of single quotes when used in the patsub PE

#!/usr/bin/env bash
for shell in bash mksh ksh zsh; do
"$shell" <<'EOF'
  t() {
    printf '%s  |  %s\n' "$1" "$2"
  }
  v="'"       # v <- '
  
  printf '===\n%s %s\n---\n' \
    "$0" \
    "$BASH_VERSION"
  
  #--
  t "${v/$'\''/$'\''}"        "'"
  t  ${v/$'\''/$'\''}         "'"
  t "${v/$'\''/x}"            "x"
  t  ${v/$'\''/x}             "x"
  t "${v/x/$'\''}"            "'"
  t  ${v/x/$'\''}             "'"
  t "${v/x/$'\x5c\''}"        "'" #< I would actually expect these to
  t  ${v/x/$'\x5c\''}         "'" #< be \'
  t "${v/\'/\'}"              "'"
  t  ${v/\'/\'}               "'"
EOF
done

Behaviour of brace expansion is different in devel branch

echo x{,}

Segmentation fault in arithmetical expression when mixing array variables

 #!/bin/bash
   
 echo "$BASH_VERSION"
 echo $(( a=(y[0] + y[1]) & 0xff, b=(y[2] + y[3]) & 0xff, a << 8 | b))
   
 # simpler
 ( y=(1 2); (( _ = y[0], _ = 1 )) ) # crash

%(fmt)T fails with large times in 64-bit linux

 for i in {56..63}; do
     printf '%s ' $i;
     bash -c 'printf %\(%s\)T\\n $((2**$1))' _ $i;
 done