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   new mir (mir@ice.ch3.st)'s status on Friday, 31-Jan-2025 17:08:53 JST new mir

   hm my program executes fine but then segfaults

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     nyanide :nyancat_rainbow::nyancat_body::nyancat_face: (nyanide@lab.nyanide.com)'s status on Friday, 31-Jan-2025 17:08:50 JST nyanide :nyancat_rainbow::nyancat_body::nyancat_face:

     in reply to

     @mir you do not need the length of the file nor do you need a buffer containing the entire file really, if you just want to print to stdout you could simplify down to these lines

     #include <stdio.h> #include <unistd.h> void cat(char *filename) { FILE *fp = fopen(filename, "r"); char c; if (fp == NULL) { fprintf(stderr, "error: unable to open file\n"); _exit(-1); } while ((c = fgetc(fp)) != EOF) putchar(c); fclose(fp); } int main(int argc, char **argv) { if (argc <= 1) { fprintf(stderr, "error: no file specified\n"); _exit(-1); } for (int i = 1; i < argc; i++) cat(argv[i]); return 0; }

     here's the implementation in action

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     new mir (mir@ice.ch3.st)'s status on Friday, 31-Jan-2025 17:08:52 JST new mir

     in reply to

     heres the program btw. test.txt and txt2.txt are files with keysmashes and copypasta in the working directory. im just running gcc mircat.c and it spits out a a.out that's executable
     /* my first C program ever! gonna make a copy of `cat` with maybe extra features idk /* */ #include <stdio.h> #include <string.h> char* greeting = "bonjour"; char *fnames[] = {"test.txt","tst2.txt"}; int catfile (char* file){ FILE *stream ; int beg ; int end ; stream = fopen(file, "r") ; // type `FILE *` fseek(stream, 0, SEEK_SET); beg = ftell (stream); // should always be 0 fseek(stream, 0, SEEK_END); end = ftell (stream); //end of file char contents[end] ; for (int i = beg; i <= end ; i++) { fseek(stream, i, SEEK_SET); // go to next position contents[i] = fgetc (stream); // get char at said pos and assign it thusly }; printf ("file %s starts at %ld and ends at %ld\nits contents follow:\n%s\n\n", file, beg, end, contents ); }; int main (){ printf ("%s\n\n", greeting); for (int i = 0; i <= 2; i++) { catfile (fnames[i]); } ; return 0; }

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     nyanide :nyancat_rainbow::nyancat_body::nyancat_face: (nyanide@lab.nyanide.com)'s status on Friday, 31-Jan-2025 17:10:13 JST nyanide :nyancat_rainbow::nyancat_body::nyancat_face:

     in reply to

     • imported green :rainforest_frog: (made in russia)
     @mir @green garbage data from unused space on the buffer?
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     new mir (mir@ice.ch3.st)'s status on Friday, 31-Jan-2025 17:10:15 JST new mir

     in reply to

     • imported green :rainforest_frog: (made in russia)

     @green now, what's with these \377 and \375 (broken characters, they render even worse in a normal terminal)

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     new mir (mir@ice.ch3.st)'s status on Friday, 31-Jan-2025 17:10:17 JST new mir

     in reply to

     • imported green :rainforest_frog: (made in russia)

     @green ope good catch

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     imported green :rainforest_frog: (made in russia) (green@ice.ch3.st)'s status on Friday, 31-Jan-2025 17:10:21 JST imported green :rainforest_frog: (made in russia)

     in reply to

     @mir int i = 0; i <= 2; i++ this actually iterates 3 times. it segfaults because it tries to read the 3rd element of the fnames array

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     new mir (mir@ice.ch3.st)'s status on Friday, 31-Jan-2025 17:14:36 JST new mir

     in reply to

     • nyanide :nyancat_rainbow::nyancat_body::nyancat_face:

     @nyanide@lab.nyanide.com i don't "just want to print to stdout". i want the option of doing other things with that buffer, even if the current code doesn't have anything for that.

     nyanide :nyancat_rainbow::nyancat_body::nyancat_face: likes this.
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     nyanide :nyancat_rainbow::nyancat_body::nyancat_face: (nyanide@lab.nyanide.com)'s status on Friday, 31-Jan-2025 17:27:48 JST nyanide :nyancat_rainbow::nyancat_body::nyancat_face:

     in reply to

     @mir no biggie then, on unix we are blessed with stat(2), which you can use to retrieve file information including but not limited to the size of a file

     #include <stdio.h> // perror is also here! #include <stdlib.h> // malloc, free #include <unistd.h> // _exit #include <sys/stat.h> #include <string.h> // memset char * cat(char *filename) { FILE *fp; char *buf; struct stat s; if (stat(filename, &s) != 0) { perror("stat"); _exit(-1); } fp = fopen(filename, "r"); if (fp == NULL) { fprintf(stderr, "error: unable to open file\n"); _exit(-1); } buf = malloc(s.st_size+1); memset(buf, s.st_size+1, 0); // fill the buffer with zeroes to ensure null termination // sizeof(char) is always 1 but i like being in the habit of writing these things for portability purposes fread(buf, sizeof(char), s.st_size, fp); fclose(fp); return buf; } int main(int argc, char **argv) { if (argc <= 1) { fprintf(stderr, "error: no file specified\n"); _exit(-1); } for (int i = 1; i < argc; i++) { char *buf = cat(argv[i]); printf("%s", buf); free(buf); buf = NULL; } return 0; }
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     nyanide :nyancat_rainbow::nyancat_body::nyancat_face: (nyanide@lab.nyanide.com)'s status on Friday, 31-Jan-2025 17:32:05 JST nyanide :nyancat_rainbow::nyancat_body::nyancat_face:

     in reply to

     • nyanide :nyancat_rainbow::nyancat_body::nyancat_face:
     @mir minor bugfix cause i forgot to check the return value of malloc lmao
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     nyanide :nyancat_rainbow::nyancat_body::nyancat_face: (nyanide@lab.nyanide.com)'s status on Friday, 31-Jan-2025 17:51:43 JST nyanide :nyancat_rainbow::nyancat_body::nyancat_face:

     in reply to

     • imported green :rainforest_frog: (made in russia)
     @green @mir >some prefer to put pointer next to type and other next to the name
     
     in c you don't really explicitly define a char*, variables are assumed char (or other type) unless you point a star next to them,
     
     you can't do char* b, a, because only b is recognized as a ptr
     
     thus it's better to put the type next to the name but like, yeah I guess personal preference
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     imported green :rainforest_frog: (made in russia) (green@ice.ch3.st)'s status on Friday, 31-Jan-2025 17:51:45 JST imported green :rainforest_frog: (made in russia)

     in reply to

     @mir here you go. i hope my voice is cute :neocat_floof_aww:

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     imported green :rainforest_frog: (made in russia) (green@ice.ch3.st)'s status on Friday, 31-Jan-2025 18:00:43 JST imported green :rainforest_frog: (made in russia)

     in reply to

     • nyanide :nyancat_rainbow::nyancat_body::nyancat_face:

     @mir@ice.ch3.st @nyanide@lab.nyanide.com the portable way to check how big a file is, would be with fseek/ftell, just like in mir's first code. also why are you using _exit instead of exit

     nyanide :nyancat_rainbow::nyancat_body::nyancat_face: likes this.
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     nyanide :nyancat_rainbow::nyancat_body::nyancat_face: (nyanide@lab.nyanide.com)'s status on Friday, 31-Jan-2025 18:01:28 JST nyanide :nyancat_rainbow::nyancat_body::nyancat_face:

     in reply to

     • imported green :rainforest_frog: (made in russia)
     @green @mir i did man 2 exit and that's what i found so i just kinda rolled with it, normally i do exit lmao
     
     also yeah I mentioned in a post edit it's not portable. I don't know if that federated.
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     imported green :rainforest_frog: (made in russia) (green@ice.ch3.st)'s status on Friday, 31-Jan-2025 18:08:36 JST imported green :rainforest_frog: (made in russia)

     in reply to

     • nyanide :nyancat_rainbow::nyancat_body::nyancat_face:

     @mir@ice.ch3.st @nyanide@lab.nyanide.com yeah, because _exit is the syscall. that's why it would be in the syscall(2) manual. the exit function in c also does other stuff, like flushing the buffers of all open files. the man section to look for c fucntions is usually 3

     nyanide :nyancat_rainbow::nyancat_body::nyancat_face: likes this.