utils-std

commit: 1c81a03d121a969d0dfe9c52f480a66554efd00d
parent 2cb594ab23dbc1cee684ee04401be431444bda69
Author: Haelwenn (lanodan) Monnier <contact@hacktivis.me>
Date:   Fri, 30 May 2025 08:42:17 +0200

cmd/printf: Add support for %q specifier

Diffstat:
M
cmd/printf.1
11
+++++++++++
M
cmd/printf.c
61
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
M
test-cmd/printf.sh
10
+++++++++-

3 files changed, 81 insertions(+), 1 deletion(-)
diff --git a/cmd/printf.1 b/cmd/printf.1
@@ -338,6 +338,13 @@ and that an additional escape sequence
 stops further output from this
 .Nm
 invocation.
+.It Cm q
+Print
+.Ar argument
+so it can be reused for shell input,
+escaping control characters and single-quote with POSIX.1-2024
+.Cm $''
+(dollar-single-quote) syntax.
 .It Cm n$
 Allows reordering of the output according to
 .Ar argument .
@@ -420,6 +427,10 @@ backslash-escapes are extensions
 inspired by
 .Xr sh 1 Ns 's
 dollar-single-quote($'…') escapes.
+.Pp
+The
+.Cm %q
+format specifier is an extension inspired by GNU coreutils.
 .Sh HISTORY
 The
 .Nm
diff --git a/cmd/printf.c b/cmd/printf.c
@@ -4,6 +4,7 @@
 
 #define _POSIX_C_SOURCE 200809L
 #include <errno.h>
+#include <stdbool.h>
 #include <stdio.h>  // printf
 #include <stdlib.h> // strtoul, strtod
 #include <string.h> // strlen, memchr
@@ -29,6 +30,12 @@ isxdigit(int c)
 	return isdigit(c) || (c >= 'A' && c <= 'F') || (c >= 'a' && c <= 'f');
 }
 
+static int
+iscntrl(int c)
+{
+	return (unsigned)c < 0x20 || c == 0x7f;
+}
+
 // len parameter needed because of NULL escapes
 // returns 1 for handling '\c' early ends
 static int
@@ -520,6 +527,60 @@ main(int argc, char *argv[])
 
 				break;
 			}
+			case 'q':
+			{
+				if(fwidth != 0)
+				{
+					fprintf(
+					    stderr,
+					    "printf: error: (format position %d) field-width is unsupported with 'q' specifier\n",
+					    (int)(fmt_idx - fmt));
+					return 1;
+				}
+
+				if(precision != -1)
+				{
+					fprintf(
+					    stderr,
+					    "printf: error: (format position %d) precision is unsupported with 'q' specifier\n",
+					    (int)(fmt_idx - fmt));
+					return 1;
+				}
+
+				size_t arglen = strlen(fmt_arg);
+				bool quoted = false;
+				for(size_t i = 0; i < arglen; i++)
+				{
+					if(!(iscntrl(fmt_arg[i]) || fmt_arg[i] == '\'' || fmt_arg[i] == '"'))
+					{
+						putchar(fmt_arg[i]);
+						continue;
+					}
+
+					if(!quoted)
+					{
+						quoted = true;
+						fputs("$'", stdout);
+					}
+
+					switch(fmt_arg[i])
+					{
+					default:
+					case 0x7F:
+						/* for control chars */
+						printf("\\c%c", fmt_arg[i] == 0x7F ? '?' : fmt_arg[i] + '@');
+						break;
+					case '\'':
+						fputs("\\'", stdout);
+						break;
+					case '"':
+						putchar(fmt_arg[i]);
+						break;
+					}
+				}
+				if(quoted) putchar('\'');
+				break;
+			}
 			case 'c':
 				printf("%*c", fwidth, *fmt_arg);
 				break;
diff --git a/test-cmd/printf.sh b/test-cmd/printf.sh
@@ -2,7 +2,7 @@
 # SPDX-FileCopyrightText: 2017 Haelwenn (lanodan) Monnier <contact+utils@hacktivis.me>
 # SPDX-License-Identifier: MPL-2.0
 
-plans=33
+plans=37
 WD="$(dirname "$0")/../"
 target="${WD}/cmd/printf"
 . "${WD}/test-cmd/tap.sh"
@@ -29,6 +29,14 @@ t_args fmt_b '
 t_args fmt_b_rightpad '!{}   .' '%-6b%c' '\041\x7B\x7d' .
 t_args fmt_b_leftpad  '   !{}.' '%6b%c'  '\041\x7B\x7d' .
 
+t_args fmt_q_print 'foo
+baré
+' '%q\n' foo baré
+t_args fmt_q_cntrl "back$'\cHdel\c?nl\cJ'" '%q' 'backdelnl
+'
+t_args fmt_q_sq "single$'\\'quote'" %q "single'quote"
+t_args fmt_q_dq "double$'"'"'"quote'" %q 'double"quote'
+
 t_args fmt_c 'foo' %c f oo oooo
 
 t_args fmt_d 10, %d, 10