61 lines
1.8 KiB
C
61 lines
1.8 KiB
C
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/* This file is part of the sample code and exercises
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* used by the class "Advanced Programming in the UNIX
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* Environment" taught by Jan Schaumann
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* <jschauma@netmeister.org> at Stevens Institute of
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* Technology.
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*
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* This file is in the public domain.
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*
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* You don't have to, but if you feel like
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* acknowledging where you got this code, you may
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* reference me by name, email address, or point
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* people to the course website:
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* https://stevens.netmeister.org/631/
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*/
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/* Students frequently think that the result of 'sizeof'
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* is equivalent to that of strlen(3). Let's illustrate
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* the differences. */
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#include <errno.h>
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#include <libgen.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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int main() {
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printf("int: %ld\n", sizeof(int));
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char buf[BUFSIZ];
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printf("Fixed buffer, size known at compile time: \"buf[%d]\"\n", BUFSIZ);
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printf("strlen: %lu - sizeof: %lu\n\n", strlen(buf), sizeof buf);
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char buf2[2] = { 'a' };
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printf("Fixed-size, initialized buffer: \"buf[2] = { 'a' }\"\n");
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printf("strlen: %lu - sizeof: %lu\n\n", strlen(buf2), sizeof buf2);
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char *s = "abcde";
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printf("A pointer: 'char *s = \"abcde\"'\n");
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printf("strlen: %lu - sizeof: %lu\n\n", strlen(s), sizeof s);
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char buf3[] = "abcde";
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printf("Another initialized buffer, implicitly sized: 'buf3[] =\"abcde\"'\n");
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printf("strlen: %lu - sizeof: %lu\n\n", strlen(buf3), sizeof buf3);
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if ((s = malloc(BUFSIZ)) == NULL) {
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fprintf(stderr, "Unable to allocate memory: %s\n",
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strerror(errno));
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exit(EXIT_FAILURE);
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}
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printf("A pointer to malloc(3)'d memory:\n");
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printf("strlen: %lu - sizeof: %lu\n\n", strlen(s), sizeof s);
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(void)strncat(s, "0123456789", BUFSIZ);
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printf("After strncat(3)ing \"0123456789\" to 's':\n");
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printf("strlen: %lu - sizeof: %lu\n\n", strlen(s), sizeof s);
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return EXIT_SUCCESS;
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}
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