diff --git a/sh/argc b/sh/argc
new file mode 100644
index 0000000..c1e4baf
--- /dev/null
+++ b/sh/argc
@@ -0,0 +1,81 @@
+#!/usr/bin/env sh
+# YES_ZSH
+# YES_BASH
+# YES_DASH
+# YES_ASH
+
+argc() { ### @-
+    ### ```sh
+    ### # usage:
+    ###
+    ### myfunc() {
+    ###     argc X "$0" "$@" || return;
+    ###     #    ^-- replace X with one of the following:
+    ###     # * N to expect an *exact* (==) number of arguments,
+    ###     # * +N to expect *at least* (>=) some number of arguments,
+    ###     # * -N to expect *at most* (<=) some number of arguments,
+    ###     # where N is an integer between 0 and 9.
+    ### }
+    ### ```
+
+    if [ $# -lt 2 ] || [ -z "$1" ] || [ -z "$2" ]; then
+        printf 'usage: %s (N|+N|-N) "$0" "$@" || return\n' "$0" >&2
+        return 2
+    fi
+
+    local want="$1"; shift
+    local zero="$1"; shift
+    local err=''
+
+    case "$want" in
+    # i realize hardcoding each case like this *looks* terrible,
+    # but consider: there's only thirty cases we need to handle.
+    # plus, i can write a specific error message for each.
+
+    0) [ $# -eq 0 ] || err='expected no arguments, got';;
+    1) [ $# -eq 1 ] || err='expected exactly one argument, got';;
+    2) [ $# -eq 2 ] || err='expected exactly two arguments, got';;
+    3) [ $# -eq 3 ] || err='expected exactly three arguments, got';;
+    4) [ $# -eq 4 ] || err='expected exactly four arguments, got';;
+    5) [ $# -eq 5 ] || err='expected exactly five arguments, got';;
+    6) [ $# -eq 6 ] || err='expected exactly six arguments, got';;
+    7) [ $# -eq 7 ] || err='expected exactly seven arguments, got';;
+    8) [ $# -eq 8 ] || err='expected exactly eight arguments, got';;
+    9) [ $# -eq 9 ] || err='expected exactly nine arguments, got';;
+
+    +0) :;; # anything goes
+    +1) [ $# -ge 1 ] || err='expected at least one argument, got';;
+    +2) [ $# -ge 2 ] || err='expected at least two arguments, got';;
+    +3) [ $# -ge 3 ] || err='expected at least three arguments, got';;
+    +4) [ $# -ge 4 ] || err='expected at least four arguments, got';;
+    +5) [ $# -ge 5 ] || err='expected at least five arguments, got';;
+    +6) [ $# -ge 6 ] || err='expected at least six arguments, got';;
+    +7) [ $# -ge 7 ] || err='expected at least seven arguments, got';;
+    +8) [ $# -ge 8 ] || err='expected at least eight arguments, got';;
+    +9) [ $# -ge 9 ] || err='expected at least nine arguments, got';;
+
+    -0) [ $# -le 0 ] || err='expected no arguments, got';;
+    -1) [ $# -le 1 ] || err='expected at most one argument, got';;
+    -2) [ $# -le 2 ] || err='expected at most two arguments, got';;
+    -3) [ $# -le 3 ] || err='expected at most three arguments, got';;
+    -4) [ $# -le 4 ] || err='expected at most four arguments, got';;
+    -5) [ $# -le 5 ] || err='expected at most five arguments, got';;
+    -6) [ $# -le 6 ] || err='expected at most six arguments, got';;
+    -7) [ $# -le 7 ] || err='expected at most seven arguments, got';;
+    -8) [ $# -le 8 ] || err='expected at most eight arguments, got';;
+    -9) [ $# -le 9 ] || err='expected at most nine arguments, got';;
+
+    *)
+        printf 'usage: %s (N|+N|-N) "$0" "$@" || return\n' "$0" >&2
+        return 2;;
+    esac
+
+    if [ -n "$err" ]; then
+        printf '%s: %s %s\n' "$zero" "$err" "$#" >&2
+        return 1
+    fi
+
+    return 0
+}
+
+[ "${SOURCING:-0}" -gt 0 ] || argc "$@"
diff --git a/sh/streamcrap b/sh/streamcrap
index 2edf088..47b6e79 100644
--- a/sh/streamcrap
+++ b/sh/streamcrap
@@ -24,7 +24,7 @@ _M_LESS_INSANE="$_M_PRE_EMPH,acompressor=threshold=0.0020:ratio=1.41:attack=1000
 _M_NEO="equalizer=700:o:1.3:-5,equalizer=1200:o:1.3:-3,equalizer=1090:o:0.5:-5,equalizer=970:o:1.2:-10,equalizer=4100:o:0.3:-6"
 
 getladspa() {
-    [ $# -eq 1 ] || { printf "%s\n" "$0: expected exactly one argument" >&2; return 1; }
+    argc 1 "$0" "$@" || return
     REPLY=volume
     if [ -e "/usr/lib/ladspa/${1}.so" ]; then
         REPLY="ladspa=f=${1}:p=${1}"
@@ -37,7 +37,7 @@ _M_LEVEL="$REPLY"
 _nn="$(uname -n | tr A-Z a-z)"
 
 earphones() {
-    [ $# -eq 0 ] || { printf "%s\n" "$0: unexpected arguments" >&2; return 1; }
+    argc 0 "$0" "$@" || return
     _M_PROCESS="lowpass=8000:p=1,$_M_KILL,alimiter=level_out=0.707"
 }
 
@@ -46,7 +46,7 @@ if [ "$_nn" = spectre ]; then
 fi
 if [ "$_nn" = neobanshee ]; then
     speakers() {
-        [ $# -eq 0 ] || { printf "%s\n" "$0: unexpected arguments" >&2; return 1; }
+        argc 0 "$0" "$@" || return
         _M_PROCESS="highpass=311,$_M_KILL,$_M_NEO,alimiter=level_in=2"
     }
     speakers
@@ -55,7 +55,7 @@ if [ "$_nn" = banshee ]; then
     getladspa crap_eq_const_T420
     _M_SPEAKERS="$REPLY"
     speakers() {
-        [ $# -eq 0 ] || { printf "%s\n" "$0: unexpected arguments" >&2; return 1; }
+        argc 0 "$0" "$@" || return
         _M_PROCESS="$_M_LEVEL,$_M_SPEAKERS,alimiter=level_in=0.5"
     }
     speakers
@@ -65,7 +65,7 @@ unset _nn
 
 mpv_watch() { ### @-
     ### watch something in mpv with a bunch of extra audio filtering crap.
-    [ $# -gt 0 ] || { printf "%s\n" "$0: too few arguments" >&2; return 1; }
+    argc +1 "$0" "$@" || return
     pushd ~/play >/dev/null
     local url="$1"; shift
     mpv \
@@ -77,7 +77,7 @@ mpv_watch() { ### @-
 
 mpv_stream() { ### @-
     ### watch a stream in mpv with a bunch of extra audio filtering crap.
-    [ $# -gt 0 ] || { printf "%s\n" "$0: too few arguments" >&2; return 1; }
+    argc +1 "$0" "$@" || return
     pushd ~/play >/dev/null
     local url="$1"; shift
     mpvs --af=lavfi="[$_M_PROCESS]" "$@" "$url"
@@ -86,7 +86,7 @@ mpv_stream() { ### @-
 
 twitch() { ### @-
     ### watch a twitch stream in mpv with a bunch of extra audio filtering crap.
-    [ $# -gt 0 ] || { printf "%s\n" "$0: too few arguments" >&2; return 1; }
+    argc +1 "$0" "$@" || return
     local user="$1"; shift
     mpv_stream "http://twitch.tv/$user" "$@"
 }
@@ -97,7 +97,7 @@ yt() { ### @-
     ### remaining arguments are passed to mpv.
     ###
     ### there exist several variants for more specific use cases.
-    [ $# -gt 0 ] || { printf "%s\n" "$0: too few arguments" >&2; return 1; }
+    argc +1 "$0" "$@" || return
     local vid="$1"; shift
     [ -e "$vid" ] || [ "$vid" != "${vid#http}" ] || vid="ytdl://$vid"
     mpv_watch "$vid" "$@"
@@ -105,7 +105,7 @@ yt() { ### @-
 
 ytg() { ### @-
     ### watch a youtube video. like `yt`, but with a preference for different formats.
-    [ $# -gt 0 ] || { printf "%s\n" "$0: too few arguments" >&2; return 1; }
+    argc +1 "$0" "$@" || return
     local vid="$1"; shift
     yt "$vid" --ytdl-format=22/95/300/best "$@"
 }
@@ -113,26 +113,26 @@ ytg() { ### @-
 ytll() { ### @-
     ### watch a stream on youtube in mpv, etcetera etcetera.
     ### this is the low latency version that does not support seeking.
-    [ $# -gt 0 ] || { printf "%s\n" "$0: too few arguments" >&2; return 1; }
+    argc +1 "$0" "$@" || return
     youtube-dl -q -f best "$1" -o - | mpv_stream - --no-ytdl
 }
 
 ytgll() { ### @-
     ### watch a stream on youtube in mpv. like `ytll`, but with a preference for different formats.
-    [ $# -gt 0 ] || { printf "%s\n" "$0: too few arguments" >&2; return 1; }
+    argc +1 "$0" "$@" || return
     youtube-dl -q -f 22/95/300/best "$1" -o - | mpv_stream - --no-ytdl
 }
 
 ai() { # @-
     # hai domo!
-    [ $# -gt 0 ] || { printf "%s\n" "$0: too few arguments" >&2; return 1; }
+    argc +1 "$0" "$@" || return
     yt "$@" --slang=en --sub-font='Tekton Pro' --sub-bold=yes \
       --sub-font-size=60 --sub-border-color='#DD6180' --sub-margin-y=52
 }
 
 asmr() { # @-
     # for your aural pleasure.
-    [ $# -gt 0 ] || { printf "%s\n" "$0: too few arguments" >&2; return 1; }
+    argc +1 "$0" "$@" || return
     _M_PROCESS="acompressor=threshold=0.001:ratio=1.33:attack=900:release=6000:makeup=6:knee=8:mix=0.9,alimiter" \
       yt "$@" --volume=90 --ytdl-format=251/300/best
 }