examples

commit 86ed3d35616d58be660771325d65f2e1e3abb0ca
parent 7f468e9155e4ea68b86dc56e85be7f29e832633c
Author: Henry Wilson <henry@henryandlizzy.uk>
Date:   Fri, 26 Aug 2022 23:42:53 +0100

enviro: Run program with environment variables set

Diffstat:
A
src/enviro.c
 | 
134
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 134 insertions(+), 0 deletions(-)
diff --git a/src/enviro.c b/src/enviro.c
@@ -0,0 +1,134 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <regex.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+
+#define ARRAY_SIZE(a)	(sizeof(a) / sizeof(*(a)))
+
+__attribute__((noreturn))
+void die(char const* msg)
+{
+	fprintf(stderr, "enviro: %s\n", msg);
+	exit(1);
+}
+
+__attribute__((noreturn))
+void errorno_die(char const* msg)
+{
+	perror(msg);
+	exit(1);
+}
+
+__attribute__((noreturn))
+void regex_die(int e, regex_t const* r, char const* msg)
+{
+	size_t size = regerror(e, r, NULL, 0);
+	char* buf = malloc(size);
+
+	regerror(e, r, buf, size);
+	fprintf(stderr, "%s: %s\n", msg, buf);
+	exit(1);
+}
+
+int regexec_or_die(const regex_t *restrict preg, const char *restrict string, size_t nmatch, regmatch_t pmatch[restrict], int eflags)
+{
+	int e = regexec(preg, string, nmatch, pmatch, eflags);
+	switch (e)
+	{
+	case REG_NOMATCH:
+	case 0:
+		return e;
+
+	default:
+		regex_die(e, preg, "regexec");
+	}
+}
+
+char const usage[] =
+	"USAGE:\n"
+	"\tenviro (file | -) command [args...]\n"
+	"\nSUMMARY:\n"
+	"\tRun command with the environment from a file or stdin\n";
+
+char const* regexes[] =
+{
+	"^[[:blank:]]*(#.*)?\n$",
+	"^[[:blank:]]*([[:alnum:]_.,]+=.*)\n$",
+};
+
+regex_t r[ARRAY_SIZE(regexes)];
+
+int main(int argc, char* argv[])
+{
+	FILE* f = stdin;
+
+	for (unsigned i = 0; i < ARRAY_SIZE(r); ++i)
+	{
+		int e = regcomp(r + i, regexes[i], REG_EXTENDED | REG_NEWLINE);
+		if (e)
+			regex_die(e, r + i, "regcomp");
+	}
+
+	if (argc < 3)
+	{
+		fputs(usage, stderr);
+		return 1;
+	}
+
+	if (strcmp("-", argv[1]))
+	{
+		struct stat s;
+		int fd = open(argv[1], O_RDONLY);
+		
+		if (fd < 0)
+			errorno_die("open");
+
+		if (fstat(fd, &s))
+			errorno_die("fstat");
+
+		if ((s.st_mode & S_IFMT) == S_IFDIR)
+		{
+			fprintf(stderr, "enviro: '%s' is a directory\n", argv[1]);
+			exit(1);
+		}
+
+		f = fdopen(fd, "r");
+		if (!f)
+			errorno_die("fdopen");
+	}
+
+	clearenv();
+
+	for (;;)
+	{
+		char* line = NULL;
+		size_t size = 0;
+		regmatch_t m[2];
+
+		if (getline(&line, &size, f) == -1)
+			break;
+
+		if (!regexec_or_die(&r[0], line, 0, NULL, 0))
+			continue;
+
+		if (regexec_or_die(r+1, line, ARRAY_SIZE(m), m, 0))
+		{
+			fprintf(stderr, "enviro: bad format: %s\n", line);
+			return 1;
+		}
+
+		if (m[1].rm_so == -1)
+			die("bad match");
+
+		line[m[1].rm_eo] = '\0';
+
+		if (putenv(line + m[1].rm_so))
+			errorno_die("putenv");
+	}
+
+	execvp(argv[2], argv + 2);
+	errorno_die("execvp");
+}