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Expansion : text replacement in a string

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Jérôme Guélen 2025-02-25 18:51:27 +01:00
parent d30a39d907
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28
interesting_tests.md Normal file
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jguelen@c2r12p1 ~()% bash
jguelen@c2r12p1:~$ export test=flagada$PATH
jguelen@c2r12p1:~$ echo $test
flagada/home/jguelen/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/usr/local/go/bin
jguelen@c2r12p1:~$ export test="flagada"$PATH
jguelen@c2r12p1:~$ echo $test
flagada/home/jguelen/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/usr/local/go/bin
jguelen@c2r12p1:~$ export test=flagada"$PATHhihi"
jguelen@c2r12p1:~$ echo $test
flagada
jguelen@c2r12p1:~$ export test=flagada"$PATH hihi"
jguelen@c2r12p1:~$ echo $test
flagada/home/jguelen/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/usr/local/go/bin hihi
jguelen@c2r12p1:~$ export test=flagada"$PATH"hihi
jguelen@c2r12p1:~$ echo $test
flagada/home/jguelen/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/usr/local/go/binhihi
jguelen@c2r12p1:~$ export test=flagada"$'PA'TH"hihi
jguelen@c2r12p1:~$ echo $test
flagada$'PA'THhihi
jguelen@c2r12p1:~$ export test=flagada$'P'ATH
jguelen@c2r12p1:~$ echo $test
flagadaPATH
jguelen@c2r12p1:~$ export test=flagada$P'A'TH hihi
jguelen@c2r12p1:~$ echo $test
flagadaATH
jguelen@c2r12p1:~/Common_Core/minishell$ echo "tests$"PATH""
tests$PATH
jguelen@c2r12p1:~$

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src/subst/replace_substr.c Normal file
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/* ************************************************************************** */
/* */
/* ::: :::::::: */
/* replace_substr.c :+: :+: :+: */
/* +:+ +:+ +:+ */
/* By: jguelen <marvin@42.fr> +#+ +:+ +#+ */
/* +#+#+#+#+#+ +#+ */
/* Created: 2025/02/25 13:02:59 by jguelen #+# #+# */
/* Updated: 2025/02/25 18:50:00 by jguelen ### ########.fr */
/* */
/* ************************************************************************** */
#include "replace_substr.h"
/*
** @RETURN Returns a new C-compliant malloc-allocated string corresponding to
** text where the substring starting in text at index index_start and ending
** at index_end is replaced in totality by the C-compliant string replacement
** excluding its NULL-byte.
** Returns NULL if an allocation error occurred.
*/
char *replace_in_str(const char *text, size_t index_start, size_t index_end,
char *replacement)
{
char *new;
size_t len_text;
size_t len_rep;
size_t new_size;
len_text = ft_strlen(text);
len_rep = ft_strlen(replacement);
new_size = len_text + index_start - index_end + len_rep;
if (index_end >= index_start)
{
new = malloc(new_size * sizeof(char));
if (!new)
return (NULL);
ft_memmove(new, text, index_start);
ft_memmove(new + index_start, replacement, len_rep);
ft_memmove(new + index_start + len_rep, text + index_end + 1,
len_text - index_end - 1);
new[new_size - 1] = '\0';
return (new);
}
return (ft_strdup(text));
}
/*
** word is presumed not to be NULL
*/
int *better_prefix_array(char *word, size_t word_len)
{
int i;
int j;
int *better_prefix;
i = 0;
better_prefix = ft_calloc(word_len + 1, sizeof(int));
if (!better_prefix)
return (NULL);
better_prefix[0] = -1;
j = 0;
while (++j < m)
{
if (word[i] == word[j])
better_prefix[j] = better_prefix[i];
else
{
better_prefix[j] = i;
i = better_prefix[i];
while (i >= 0 && word[j] != word[i])
i = better_prefix[i];
}
i++;
}
better_prefix[word_len] = i;
return (better_prefix);
}
/*
** Return the index at which the word needle begins in haystack if found,
** -1 if needle is not to be found in haystack.
*/
ssize_t find_word_index(const char *haystack, char *needle)
{
int i;
int j;
size_t len_n;
int *better_prefix;
i = 0;
j = 0;
len_n = ft_strlen(needle);
better_prefix = better_prefix_array(needle, len_n);
while (haystack[j])
{
while (i >= 0 && needle[i] != haystack[j])
i = better_prefix[i];
i++;
if (i == len_n)
return (free(better_prefix), j);
i = better_prefix[i];
j++;
}
free(better_prefix);
return (-1);
}
/*
** @RETURN Returns a new C-compliant malloc-allocated string corresponding to
** the C-compliant string text where the first occurrence of the C-compliant
** string to_replace (NULL-byte excluded) found in text is replaced by the
** C-compliant string replacement.
** Returns NULL if an allocation error occurred.
*/
char *replace_substr(const char *text, char *to_replace, char *replacement)
{
char *new;
size_t start_index;
size_t len_torep;
len_torep = ft_strlen(to_replace);
if (len_torep)
{
start_index = find_word_index(text, to_replace);
if (start_index != -1)
return (replace_in_str(text, index_start,
(size_t)start_index + len_torep - 1, replacement));
}
return (ft_strdup(text));
}

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/* ************************************************************************** */
/* */
/* ::: :::::::: */
/* replace_substr.h :+: :+: :+: */
/* +:+ +:+ +:+ */
/* By: jguelen <jguelen@student.42.fr> +#+ +:+ +#+ */
/* +#+#+#+#+#+ +#+ */
/* Created: 2025/02/25 12:48:39 by jguelen #+# #+# */
/* Updated: 2025/02/25 13:03:51 by jguelen ### ########.fr */
/* */
/* ************************************************************************** */
#include "libft.h"
char *replace_in_str(char *text, size_t index_start, size_t index_end,
char *replacement);
char *replace_substr(char *text, char *to_replace, char *replacement);