Translate apf(1) to POSIX sh

We lose the ability to include newlines in options, but probably a
pretty good tradeoff, especially since it makes the *rc files
hand-editable in theory.

Also add skipping comments and blank lines.

Update ISSUES.markdown. There are two more Bash scripts left; one of
them, han(1), does actually require Bash, though.

4 files changed, 80 insertions, 59 deletions

diff --git a/ISSUES.markdown b/ISSUES.markdown
index 72b87ea8..b94ab582 100644
--- a/ISSUES.markdown
+++ b/ISSUES.markdown
@@ -13,7 +13,6 @@ Known issues
     -   Mostly done now:
 
         [tom@conan:~/.dotfiles/bin](git:master)$ grep bash *
-        apf:#!/usr/bin/env bash
         eds:#!/usr/bin/env bash
         han:#!/usr/bin/env bash
 
diff --git a/README.markdown b/README.markdown
index b443d618..47197122 100644
--- a/README.markdown
+++ b/README.markdown
@@ -380,7 +380,7 @@ Installed by the `install-bin` target:
         for unfolding HTTP headers, but it should work for most RFC 822
         formats.
 *   `apf(1)` prepends arguments to a command with ones read from a file,
-    intended as a framework for shell functions.
+    intended as a framework for shell wrappers or functions.
 *   `ax(1)` evaluates an awk expression given on the command line; this is
     intended as a quick way to test how Awk would interpret a given expression.
 *   `bel(1)` prints a terminal bell character.
diff --git a/bin/apf b/bin/apf
index 733d67fc..0a0cbeea 100755
--- a/bin/apf
+++ b/bin/apf
@@ -1,30 +1,52 @@
-#!/usr/bin/env bash
-# Prepend arguments from a file to a command call
+#!/bin/sh
+# Prepend arguments from a file to the given arguments for a command
 self=apf
 
-# Give up completely if no BASH_VERSINFO (<2.0)
-[ -n "$BASH_VERSINFO" ] || exit
-
-# Require at least two arguments, give usage otherwise
-if (($# < 2)) ; then
+# Require at least two arguments
+if [ "$#" -lt 2 ] ; then
     printf >&2 '%s: Need an arguments file and a command\n' "$self"
     exit 2
 fi
 
 # First argument is the file containing the null-delimited arguments
-argfile=$1
-shift
+argf=$1 cmd=$2
+shift 2
 
-# Read all the null-delimited arguments from the file
-declare -a args
-while IFS= read -rd '' arg ; do
-    args[${#args[@]}]=$arg
-done < "$argfile"
+# If the file exists, we'll read it. If it doesn't, this is not an error (think
+# personal config files like ~/.vimrc)
+if [ -f "$argf" ] ; then
 
-# Next argument is the command to run
-cmd=$1
-shift
+    # Create a temporary directory with name in $td, and handle POSIX-ish traps to
+    # remove it when the script exits.
+    td=
+    cleanup() {
+        [ -n "$td" ] && rm -fr -- "$td"
+        if [ "$1" != EXIT ] ; then
+            trap - "$1"
+            kill "-$1" "$$"
+        fi
+    }
+    for sig in EXIT HUP INT TERM ; do
+        # shellcheck disable=SC2064
+        trap "cleanup $sig" "$sig"
+    done
+    td=$(mktd "$self") || exit
+    
+    # Write the arguments in reverse to a temporary file
+    revf=$td/revf
+    sed '1!G;$!{h;d}' "$argf" > "$revf" || exit
+    
+    # Stack up all the arguments from the file. Skip blank lines and comments.
+    # An empty file is also fine.
+    while IFS= read -r arg ; do
+        case $arg in
+            '#'*) continue ;;
+            *[![:space:]]*) ;;
+            *) continue ;;
+        esac
+        set -- "$arg" "$@"
+    done < "$revf"
+fi
 
-# Run the command with the retrieved arguments first, then the rest of the
-# command line as passed to the function
-command "$cmd" "${args[@]}" "$@"
+# Run the command with the changed arguments
+exec "$cmd" "$@"
diff --git a/man/man1/apf.1 b/man/man1/apf.1
index 67b3b25a..7cb2ab28 100644
--- a/man/man1/apf.1
+++ b/man/man1/apf.1
@@ -7,30 +7,34 @@
 foorc
 foo --bar baz
 .SH DESCRIPTION
-Add null-delimited arguments read from a file to a command's arguments before
-running it. This is intended as a way of implementing *rc files for interactive
-shell calls to programs that don't support such files, without having to use
-broken environment variables (e.g. GREP_OPTIONS); this enables you to, for
-example, use arguments with shell metacharacters and spaces in them that you do
-not want expanded.
-
+Add newline-delimited arguments read from a file to a command's arguments
+(before any given ones) before running it. This is intended as a quick way of
+implementing *rc files for interactive shell calls to programs that don't
+support such files, without having to use broken environment variables like GNU
+grep(1)'s GREP_OPTIONS.
+.P
+This enables you to use arguments with shell metacharacters and spaces in them
+that you do not want expanded. The only exception is that you cannot have
+newlines in any of the arguments. This was done to keep POSIX sh(1)
+compatibility.
+.P
 For example, given this simple program in our $PATH, printargs:
-
-    $ cat ~/.local/bin/printargs
+.P
+    $ cat /usr/bin/printargs
     #!/bin/sh
-    printf '%s\n' "$@"
-
+    printf '%s\\n' "$@"
+.P
 Which just prints its arguments:
-
+.P
     $ printargs a b c
     a
     b
     c
-
+.P
 We could do this:
-
-    $ printf '%s\0' -f --flag --option '? foo bar *' > "$HOME"/.printargsrc
-
+.P
+    $ printf '%s\\n' -f --flag --option '? foo bar *' > "$HOME"/.printargsrc
+.P
     $ apf "$HOME"/.printargsrc printargs a b c
     -f
     --flag
@@ -39,27 +43,23 @@ We could do this:
     a
     b
     c
-
-We could then make a permanent wrapper function with:
-
+.P
+We could then make a permanent wrapper script in two line:
+.P
+    $ cat >~/.local/bin/printargs
+    #!/bin/sh
+    exec apf "$HOME"/.printargsrc /usr/bin/printargs
+    ^D
+    $ chmod +x ~/.local/bin/printargs
+.P
+Or just a shell function, if it's needed interactively:
+.P
     $ printargs() { apf "$HOME"/.printargsrc printargs "$@" ; }
-
-    $ printargs a b c
-    -f
-    --flag
-    --option
-    ? foo bar *
-    a
-    b
-    c
-
-    $ printf '%s\n' !-2:q >> "$HOME"/.bashrc
-
-This means you can edit the options in the *rc file, and don't have to redefine
-a wrapper function.
-
-If you actually want those options to *always* be added, regardless of whether
-you're in an interactive shell, you really should make an actual wrapper
-script.
+.P
+It's not considered an error if the file doesn't exist or is empty. If it's a
+directory or otherwise not byte-readable, an error will be printed to stderr,
+but execution of the called program will continue anyway. Blank lines or lines
+beginning with # are also ignored. Both leading and trailing whitespace is
+preserved.
 .SH AUTHOR
 Tom Ryder <tom@sanctum.geek.nz>