I wrote a code which has to display main parameters, but when I compiled it and typed in "*" program shows my file structure.
Command in cmd looks like this: program.exe 1 2 3 *
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char const* argv[]) {
for (int i=0; i<argc; i++) printf("%s\n", argv[i]);
return 0;
}
The result is:
program
1
2
3
program.c
program.exe
10-03-20
11-02-20
And my question: Is it possible to force program to print "*" instead of listing files.
mingw causes the program to perform wildcard expansion of the parameters. Add the following to your program to disable this behaviour:
int _CRT_glob = 0;
In the unix world, the shell is expected to perform wildcard expansion.
$ perl -le'print for #ARGV' *
a
b
In the Windows world, wildcard expansion is left to the application.
>perl -le"print for #ARGV" *
*
That makes writing portable programs tricky. Since mingw is often used to compile programs that weren't written with Windows in mind, its C runtime library performs wildcard expansion of the parameters automatically.
a.c:
#include <stdio.h>
int main(int argc, char const* argv[]) {
for (int i=0; i<argc; i++)
printf("%s\n", argv[i]);
return 0;
}
>gcc -Wall -Wextra -pedantic-errors a.c -o a.exe & a *
a
a.c
a.exe
But, mingw provides an out. Adding the following to your program disables this behaviour:
int _CRT_glob = 0;
a.c:
#include <stdio.h>
int _CRT_glob = 0;
int main(int argc, char const* argv[]) {
for (int i=0; i<argc; i++)
printf("%s\n", argv[i]);
return 0;
}
>gcc -Wall -Wextra -pedantic-errors a.c -o a.exe & a *
a
*
Related
I am learning c and trying to build using makefile. I am stuck on the following error and don't know what to do next.
the build command is
gcc -o logfind logfind.o cmdargutils.o filesystem_utils.o file_utils.o strutils.o
If I need both file_utils.o and cmdargutils.o but if I add both I get the following error.
error screenshot
ERROR
file_utils.o:(.rodata+0x0): multiple definition of `MAX_LINE'
logfind.o:(.rodata+0x0): first defined here
collect2: error: ld returned 1 exit status
Makefile:2: recipe for target 'logfind' failed
make: *** [logfind] Error 1
The source is:
Makefile
logfind: clean logfind.o
gcc -o logfind logfind.o cmdargutils.o filesystem_utils.o file_utils.o strutils.o
logfind.o: logfind.c cmdargutils.o file_utils.o filesystem_utils.o strutils.o error_codes.h
gcc -c logfind.c
cmdargutils.o: cmdargutils.c cmdargutils.h
gcc -c cmdargutils.c
file_utils.o: file_utils.c file_utils.h
gcc -c file_utils.c
filesystem_utils.o: filesystem_utils.c filesystem_utils.h
gcc -c filesystem_utils.c
strutils.o: strutils.c strutils.h
gcc -c strutils.c
clean:
rm -f *.o logfind
cmdargutils.h
#ifndef CMD_ARG_UTILS
#define CMD_ARG_UTILS
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <stdbool.h>
#include "error_codes.h"
#include "strutils.h"
struct Argument {
bool is_and_operation;
int count;
char **search_terms;
};
struct Argument *argument_create(int argc, char **argv, int start, bool is_and_operation);
void argument_destroy(struct Argument *argument);
struct Argument *parse_arguments(int argc, char **argv);
#endif
error_codes.h
#ifndef ERROR_CODES
#define ERROR_CODES
enum error_codes {
MEMORY_ERROR,
INPUT_ERROR
};
#endif
file_utils.h
#ifndef FILE_UTILS
#define FILE_UTILS
#define _GNU_SOURCE
#include <stdio.h>
#include <stdbool.h>
#include <string.h>
#include <stdlib.h>
#include "cmdargutils.h"
const size_t MAX_LINE = 1024;
bool is_match(char *, struct Argument *);
bool scan_file(char *, struct Argument *);
#endif
filesystem_utils.h
#ifndef FILESYSTEM_UTILS
#define FILESYSTEM_UTILS
#include <glob.h>
#include <string.h>
#include "strutils.h"
struct SearchFiles {
int count;
char **paths;
};
struct SearchFiles *search_files_create(int count, char** paths);
void search_files_destroy(struct SearchFiles *search_files);
struct SearchFiles *scan_directory(char *directory_path, char *pattern);
#endif
strutils.h
#ifndef STRUTILS
#define STRUTILS
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "error_codes.h"
char *strdup(const char *source);
char **copy_string_array(char **source, int start, int end);
#endif
logfind.c
#include <stdio.h>
#include <stdlib.h>
#include <glob.h>
#include "cmdargutils.h"
#include "filesystem_utils.h"
#include "file_utils.h"
int main(int argc, char **argv) {
struct Argument *argument = parse_arguments(argc, argv);
int i = 0;
struct SearchFiles *search_files = scan_directory(".", "*.*");
for(i = 0; i < search_files->count; i++) {
scan_file(search_files->paths[i], argument);
}
search_files_destroy(search_files);
argument_destroy(argument);
return 0;
}
cmdargutils.c
#include "cmdargutils.h"
struct Argument *argument_create(int argc, char **argv, int start, bool is_and_operation){
struct Argument *argument = (struct Argument *)malloc(sizeof(struct Argument));
if(!argument) {
printf("Could not initialize arguments.\n");
exit(MEMORY_ERROR);
}
argument->count = argc - start;
argument->is_and_operation = is_and_operation;
argument->search_terms = copy_string_array(argv, start, argc);
return argument;
}
void argument_destroy(struct Argument *argument){
int i = 0;
for(i = 0; i < argument->count; i++) {
free(argument->search_terms[i]);
}
free(argument->search_terms);
free(argument);
argument = NULL;
}
struct Argument *parse_arguments(int argc, char **argv) {
struct Argument *argument = NULL;
bool is_and_operation = true;
int start = 0;
if(argc < 2) {
printf("Not enough arguments\n");
exit(INPUT_ERROR);
}
char *operation = argv[1];
if(strcmp(operation, "-o") == 0) {
is_and_operation = false;
if(argc < 3) {
printf("Not enough arguments\n");
exit(INPUT_ERROR);
}
}
start = is_and_operation ? 1 : 2;
argument = argument_create(argc, argv, start, is_and_operation);
return argument;
}
file_utils.c
#include "file_utils.h"
bool is_match(char *line, struct Argument *argument) {
int i = 0;
bool isMatch = false;
for(i = 0; i < argument->count; i++) {
char *found = strcasestr(line, argument->search_terms[i]);
if(!found) {
if(argument->is_and_operation) {
isMatch = false;
break;
} else {
continue;
}
} else {
isMatch = true;
if(argument->is_and_operation) {
continue;
} else {
break;
}
}
}
return isMatch;
}
bool scan_file(char *path, struct Argument *argument) {
FILE *file = fopen(path, "r");
int line_number = 0;
char *line = malloc(MAX_LINE);
while(fgets(line, MAX_LINE - 1, file)!= NULL) {
++line_number;
if(is_match(line, argument)) {
printf("%s:%d\n", path, line_number);
printf("\t%s\n", line);
}
}
free(line);
fclose(file);
}
filesystem_utils.c
#include "filesystem_utils.h"
struct SearchFiles *search_files_create(int count, char** paths) {
struct SearchFiles *search_files = (struct SearchFiles *)malloc(sizeof(struct SearchFiles));
search_files->count = count;
search_files->paths = copy_string_array(paths, 0, count);
return search_files;
}
void search_files_destroy(struct SearchFiles *search_files) {
int i = 0;
for(i = 0; i < search_files->count; i++) {
free(search_files->paths[i]);
}
free(search_files->paths);
free(search_files);
search_files = NULL;
}
struct SearchFiles *scan_directory(char *directory_path, char *pattern) {
glob_t globbuf;
int error = glob(pattern, GLOB_MARK, NULL, &globbuf);
if(!error) {
struct SearchFiles *search_files = search_files_create(globbuf.gl_pathc, globbuf.gl_pathv);
globfree(&globbuf);
return search_files;
}
return NULL;
}
strutils.c
#include "strutils.h"
char *strdup(const char *source) {
char *dest = malloc(strlen(source) + 1);
if(!dest) {
printf("Memory allocation error\n");
exit(MEMORY_ERROR);
}
strcpy(dest, source);
return dest;
}
char **copy_string_array(char **source, int start, int end) {
char **dest = (char **)malloc(sizeof(char *) * (end - start));
int di = 0;
int si = start;
for(di = 0, si = start; si < end;
si++, di++) {
dest[di] = strdup(source[si]);
}
return dest;
}
read documentation!
First, take a few hours to read documentation of GNU make, and read how to invoke GCC. You also need to understand more about the preprocessor, so read documentation of cpp. You want to take advantage of builtin GNU make rules (so run make -p to understand them) and variables. See also this answer. You could use remake (as remake -x) to debug your Makefile. You apparently don't understand how make and how gcc should be used, so you need to read more. Read also a C tutorial, look into some C reference, and glance when needed into the C11 standard n1570. Of course, read the documentation of every function you use (e.g. printf(3) etc..). For Linux system programming, read a book like ALP and relevant man pages from syscalls(2) and intro(3) etc...
Then read How to debug small programs. You certainly want to compile with all warnings and debug info.
a better Makefile
You might try something like:
# a better Makefile
# your C compiler
CC= gcc
# the verbose remove
RM= rm -vf
# your C compilation flags
CFLAGS= -Wall -Wextra -g
# your C source files
MY_CSOURCES= logfind.c cmdargutils.c filesystem_utils.c file_utils.c strutils.c
# the corresponding object files
MY_OBJECTS= $(patsubst %.c, %.o, $(MY_CSOURCES))
# the conventional phony targets
.PHONY: all clean
# the only program is for the default target all
all: logfind
logfind: $(MY_OBJECTS)
$(LINK.c) $< -o $#
# cleaning the mess
clean:
$(RM) logfind *.o *~
Of course, you need dependencies for object files on header files. You could compute them automatically, but it is simpler to explicit them, so add something like:
strutils.o: strutils.c strutils.h
and so on for each other object files.
BTW my HelloWorld/ directory on github is a tutorial example for using make
your multiple definition bug
You are getting multiple definition of MAX_LINE because it is defined in a header file included by several translation units, hence several translation units define it.
So either make it a preprocessor constant #define MAX_LINE 1024 in your header file_utils.h, or put there only a declaration like extern const int MAX_LINE; and define it only once in a single translation unit, as const int MAX_LINE=1024; in file_utils.c
general hints
I strongly recommend doing some iterative and incremental development: code only one or two dozen lines at once, then compile them, improve them to get no warnings, debug them with the GDB debugger and test them. At last repeat all this till satisfied. I do recommend using also a version control system (like git) even for school homework.
You might want to use valgrind to hunt memory leaks and other dynamic memory allocation bugs.
You could also use some static source analyzer like clang-analyzer or even Frama-C.
Once your program is debugged, you might add optimization flags like -O2 into your CFLAGS (in particular if you benchmark it with time(1)).
You could be interested by ntfw(3).
Hi im trying to figure out how to use realloc. I have made a small test project that im trying to malloc for the creation of the first element in main, followed by adding a number to that location then reallocating the array to hold one more element.
Main.c
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char *argv[]){
int i =0;
int *fileTest = (int*) malloc(sizeof(char * ));
int amtFiles=0;
for(i=0;i<3;i++){
parseInput(fileTest , amtFiles);
printf("%d", fileTest[1]);
}
}
parse.c
#include <stdlib.h>
#include "stddef.h";
#include <stdlib.h>
extern int parseInput(int *fileTest,int amtFiles){
printf("enter number");
scanf("%d",amtFiles);
fileTest = realloc(fileTest, (amtFiles * sizeof(char *)));
}
makefile
CC = gcc
CC_FLAGS = -g -ansi -pedantic -Wall -w
FILES = main.c parse.c
OUT_EXE = Test2
build: $(FILES)
$(CC) $(CC_FLAGS) -o $(OUT_EXE) $(FILES)
clean:
rm -f *.o core *.exe *~
rebuild: clean build
C is pass by value. You should return the pointer value. Otherwise the original one is unchanged. So from parseInput return the pointer or pass address of the variable and change it accordingly (not shown in example).
While reallocating use another pointer variable other than the original one, in case of failure you don't lose reference to the old memory.
Don't print uninitialized value. (in main()).
Don't cast the return value of malloc.
When printing a pointer do this printf("%p",(void*)fileTest[1]);.
Also you should put the extern declaration in main.c. You have passed incorrect number of arguments to the parseInput function. The code didn' compile.
Then after correcting the input - if you try then you might get segmentation fault or some similar error.
I have tried demonstrating something over here. The naming can be much more better. I have tried to keep the general aspects of what you have tried. Multiple source file with realloc used and tested, working with pointers etc.
main.c
#include <stdio.h>
#include <stdlib.h>
#include "myheader.h"
int main(void)
{
int *fileTest = NULL;
int amtFiles;
int weTried = 2;
while(weTried --> 0){
printf("%s\n", "Enter the array size.\n");
if( scanf("%d",&amtFiles) != 1){
fprintf(stderr, "%s\n","Error in input" );
exit(1);
}
else if( amtFiles <= 0){
fprintf(stderr, "%s\n", "Enter positive integral value");
exit(1);
}
fileTest = parseInput(fileTest, amtFiles);
if( fileTest == NULL){
fprintf(stderr, "%s\n","Realloc failed." );
exit(1);
}
for(int i = 0; i < amtFiles; i++){
printf("[%d]\n",fileTest[i]);
}
}
return 0;
}
parse.c
#include <stdlib.h>
#include <stdio.h>
#include "myheader.h"
int* parseInput(int *fileTest,int amtFiles)
{
if( amtFiles <= 0){
fprintf(stderr, "%s\n", "Error in number of inputs");
exit(1);
}
int *t = realloc(fileTest, (amtFiles * sizeof * t));
if( t == NULL ){
fprintf(stderr, "%s\n", "Execution exception");
return NULL;
}
fileTest = t;
for(int i = 0; i < amtFiles; i++){
fileTest[i] = 2017+i;
}
return fileTest;
}
myheader.h
extern int* parseInput(int *,int );
Compiled and run
gcc -Wall -Wextra -Werror main.c parse.c
./a.out
I am writing a shell script that needs to differ its behavior and provide different options to called programs based on the presence or absence of particular X11 extensions. I have a working solution, but I am hoping for a cleaner solution. I am open to considering a simple c program to do the test and return the result. Here is what I have working as a minimal functional example:
#!/bin/sh
xdpyinfo |sed -nr '/^number of extensions/,/^[^ ]/s/^ *//p' | \
grep -q $EXTENSION && echo present
I think there is a way to simplify the sed,grep but I really would prefer not to parse xdpyinfo.
You have the C-tag, too, so let me suggest to do the xdpyinfo yourself. The following C program prints just the extensions:
#include <X11/Xlib.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
static int compare(const void *a, const void *b)
{
return strcmp(*(char **) a, *(char **) b);
}
static void print_extension_info(Display * dpy)
{
int n = 0, i;
char **extlist = XListExtensions(dpy, &n);
printf("number of extensions: %d\n", n);
if (extlist) {
qsort(extlist, n, sizeof(char *), compare);
for (i = 0; i < n; i++) {
printf(" %s\n", extlist[i]);
}
}
// TODO: it might not be a good idea to free extlist, check
}
int main()
{
Display *dpy;
char *displayname = NULL;
dpy = XOpenDisplay(displayname);
if (!dpy) {
fprintf(stderr, "Unable to open display \"%s\".\n",
XDisplayName(displayname));
exit(EXIT_FAILURE);
}
print_extension_info(dpy);
XCloseDisplay(dpy);
exit(EXIT_SUCCESS);
}
Compile with e.g.: GCC
gcc -O3 -g3 -W -Wall -Wextra xdpyinfo1.0.2.c $(pkg-config --cflags --libs x11) -o xdpyinfo1.0.2
(should give a warning about unused argc but that's harmless)
Just change the printf()'s to the format you want.
Consider this program:
#include <stdio.h>
int main(int argc, char* argv[]) {
printf("%s\n", argv[1]);
return 0;
}
I compile it like this:
x86_64-w64-mingw32-gcc -o alpha alpha.c
The problem is if I give it a non ASCII argument:
$ ./alpha róisín
r�is�n
How can I write and/or compile this program such that it accepts non ASCII
characters? To respond to alk: no, the program is printing wrongly. See
this example:
$ echo Ω | od -t x1c
0000000 ce a9 0a
316 251 \n
0000003
$ ./alpha Ω | od -t x1c
0000000 4f 0d 0a
O \r \n
0000003
The easiest way to do this is with wmain:
#include <fcntl.h>
#include <stdio.h>
int wmain (int argc, wchar_t** argv) {
_setmode(_fileno(stdout), _O_WTEXT);
wprintf(L"%s\n", argv[1]);
return 0;
}
It can also be done with GetCommandLineW; here is a simple version of the code
found at the HandBrake repo:
#include <stdio.h>
#include <windows.h>
int get_argv_utf8(int* argc_ptr, char*** argv_ptr) {
int argc;
char** argv;
wchar_t** argv_utf16 = CommandLineToArgvW(GetCommandLineW(), &argc);
int i;
int offset = (argc + 1) * sizeof(char*);
int size = offset;
for (i = 0; i < argc; i++)
size += WideCharToMultiByte(CP_UTF8, 0, argv_utf16[i], -1, 0, 0, 0, 0);
argv = malloc(size);
for (i = 0; i < argc; i++) {
argv[i] = (char*) argv + offset;
offset += WideCharToMultiByte(CP_UTF8, 0, argv_utf16[i], -1,
argv[i], size-offset, 0, 0);
}
*argc_ptr = argc;
*argv_ptr = argv;
return 0;
}
int main(int argc, char** argv) {
get_argv_utf8(&argc, &argv);
printf("%s\n", argv[1]);
return 0;
}
Since you're using MinGW (actually MinGW-w64, but that shouldn't matter in this case), you have access to the Windows API, so the following should work for you. It could probably be cleaner and actually tested properly, but it should provide a good idea at the least:
#define _WIN32_WINNT 0x0600
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <wchar.h>
#include <windows.h>
int main (void)
{
int argc;
int i;
LPWSTR *argv;
argv = CommandLineToArgvW(GetCommandLineW(), &argc);
if (argv == NULL)
{
FormatMessageA(
(
FORMAT_MESSAGE_ALLOCATE_BUFFER |
FORMAT_MESSAGE_FROM_SYSTEM |
FORMAT_MESSAGE_IGNORE_INSERTS),
NULL,
GetLastError(),
0,
(LPWSTR)&error, 0,
NULL);
fprintf(stderr, error);
fprintf(stderr, "\n");
LocalFree(error);
return EXIT_FAILURE;
}
for (i = 0; i < argc; ++i)
wprintf(L"argv[%d]: %ls\n", i, argv[i]);
// You must free argv using LocalFree!
LocalFree(argv);
return 0;
}
Bear in mind this one issue with it: Windows will not compose your strings for you. I use my own Windows keyboard layout that uses combining characters (I'm weird), so when I type
example -o àlf
in my Windows Command Prompt, I get the following output:
argv[0]: example
argv[1]: -o
argv[2]: a\u0300lf
The a\u0300 is U+0061 (LATIN SMALL LETTER A) followed by a representation of the Unicode code point U+0300 (COMBINING GRAVE ACCENT). If I instead use
example -o àlf
which uses the precomposed character U+00E0 (LATIN SMALL LETTER A WITH GRAVE), the output would have differed:
argv[0]: example
argv[1]: -o
argv[2]: \u00E0lf
where \u00E0 is a representation of the precomposed character à represented by Unicode code point U+00E0. However, while I may be an odd person for doing this, Vietnamese code page 1258 actually includes combining characters. This shouldn't affect filename handling ordinarily, but there may be some difficulty encountered.
For arguments that are just strings, you may want to look into normalization with the NormalizeString function. The documentation and examples linked in it should help you to understand how the function works. Normalization and a few other things in Unicode can be a long journey, but if this sort of thing excites you, it's also a fun journey.
Try compiling and running the following program:
#include <stdio.h>
int main()
{
int i = 0;
for( i=0; i<256; i++){
printf("\nASCII Character #%d:%c ", i, i);
}
printf("\n");
return 0;
}
In your output you should see those little question marks from number 128 and onward. FYI I am using Ubuntu, and when I compile and run this program (whith GNOME Terminal) this happens to me as well.
However, if I go to Terminal > Set character encoding... and select Western (WINDOWS-1252) as opposed to Unicode (UTF-8), and rerun the program, the extended ASCII characters display properly.
I don't know the exact steps for Windows/MinGW, but, in short, changing the character encoding should fix your problem.
I want to create a shell file using the c language programming. I have this scheleton given already by the professor, but wen I try to executed I have this error and I have this problem
the myshell.c file (and this file is the one that I have to modify and execute)
/* RCS information: $Id: myshell.c,v 1.2 2006/04/05 22:46:33 elm Exp $ */
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <errno.h>
extern char **getcmdstring(char *cmd);
int main(void) {
int i;
char **args;
char cmd[4096];
while(1) {
printf("$ ");
fgets(cmd,4096,stdin);
args = getcmdstring(cmd);
for(i = 0; args[i] != NULL; i++) {
printf("Argument %d: %s\n", i, args[i]);
}
}
}
and the shell.l file
/* RCS information: $Id: shell.l,v 1.1 2006/04/05 22:46:33 elm Exp $ */
#include <stdio.h>
#include <strings.h>
#include <string.h>
int _numargs = 200;
char *_args[200];
int _argcount = 0;
char *strdup(const char *);
%}
WORD [a-zA-Z0-9\/\.-]+
SPECIAL [()><|&;]
%%
_argcount = 0; _args[0] = NULL;
{WORD}|{SPECIAL} {
if(_argcount < _numargs-1) {
_args[_argcount++] = (char *)strdup(yytext);
_args[_argcount] = NULL;
}
}
\n return (int)_args;
[ \t]+
.
%%
char **getcmdstring(char *cmd) {
char **ret;
yy_scan_string(cmd);
ret = (char **)yylex();
yy_delete_buffer(YY_CURRENT_BUFFER);
return ret;
}
The missing function is included in the shell.l source. This is a source for a lexical analyzer. You need to build the shell.o object file from shell.l.
This can be done by creating the C source
flex -o shell.c shell.l
and then compiling
clang shell.c myshell.c -o myshell -ll