Unify shell script style

bin/imgresize.sh

@@ -1,5 +1,5 @@
 #!/bin/sh
-# env
+# imgresize
 # Written in 2019 by Lucas
 # CC0 1.0 Universal/Public domain - No rights reserved
 #
@@ -10,7 +10,8 @@
 # Dedication along with this software. If not, see
 # <http://creativecommons.org/publicdomain/zero/1.0/>.
 
-usage() {
+usage()
+{
 	cat - <<. >&2
 Usage:
 	${0##*/} size in-file out-file
@@ -20,24 +21,21 @@ Usage:
 	exit 1
 }
 
-check_dimension_format() {
+err()
+{
+	printf "%s: %s\n" "${0##*/}" "$*" >&2
+	exit 1
+}
+
+check_dimension_format()
+{
 	printf "%s\n" "$1" | grep -q "^[0-9]*x[0-9]*\$" \
 	    && [ "$1" != "x" ]
 }
 
-if [ $# -ne 3 ] || ! check_dimension_format "$1"; then
-	usage
-fi
-if [ -z "$2" ]; then
-	printf "%s: Input file name can't be empty.\n" \
-	    "${0##*/}" >&2
-	exit 1
-fi
-if [ -z "$3" ]; then
-	printf "%s: Output file name can't be empty.\n" \
-	    "${0##*/}" >&2
-	exit 1
-fi
+[ $# -eq 3 ] && check_dimension_format "$1" || usage
+[ -n "$2" ] || err "Input file name can't be empty."
+[ -n "$3" ] || err "Output file name can't be empty."
 
 size=$1
 w=${size%x*}
@@ -52,8 +50,7 @@ case $infile in
 	;;
 *.png)	inprog=pngtopam
 	;;
-*)	printf "%s: Unknown input format.\n" "${0##*/}" >&2
-	exit 1
+*)	err "Unknown input format."
 	;;
 esac
 
@@ -64,8 +61,7 @@ case $outfile in
 	;;
 *.png)	outprog=pamtopng
 	;;
-*)	printf "%s: Unknown output format.\n" "${0##*/}" >&2
-	exit 1
+*)	err "Unknown output format."
 	;;
 esac