Enrico Fraccaroli (Galfurian)
117 lines
4.1 KiB
C
117 lines
4.1 KiB
C
/// @file echo.c
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/// @brief
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/// @copyright (c) 2014-2024 This file is distributed under the MIT License.
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/// See LICENSE.md for details.
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include <sys/bitops.h>
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#define ENV_NORM 1
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#define ENV_BRAK 2
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#define ENV_PROT 3
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void expand_env(char *str, char *buf, size_t buf_len, int first_word, int last_word)
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{
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// Buffer where we store the name of the variable.
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char buffer[BUFSIZ] = { 0 };
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// Flags used to keep track of the special characters.
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unsigned flags = 0;
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// We keep track of where teh
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char *env_start = NULL;
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// Where we store the retrieved environmental variable value.
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char *ENV = NULL;
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// Get the length of the string.
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size_t str_len = strlen(str);
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// Position where we are writing on the buffer.
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int b_pos = 0;
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// Iterate the string.
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for (int s_pos = 0; s_pos < str_len; ++s_pos) {
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if (first_word && (s_pos == 0) && str[s_pos] == '"')
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continue;
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if (last_word && (s_pos == (str_len - 1)) && str[s_pos] == '"')
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continue;
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// If we find the backslash, we need to protect the next character.
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if (str[s_pos] == '\\') {
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if (bit_check(flags, ENV_PROT))
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buf[b_pos++] = '\\';
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else
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bit_set_assign(flags, ENV_PROT);
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continue;
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}
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// If we find the dollar, we need to catch the meaning.
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if (str[s_pos] == '$') {
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// If the previous character is a backslash, we just need to print the dollar.
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if (bit_check(flags, ENV_PROT)) {
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buf[b_pos++] = '$';
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} else if ((s_pos < (str_len - 2)) && ((str[s_pos + 1] == '{'))) {
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// Toggle the open bracket method of accessing env variables.
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bit_set_assign(flags, ENV_BRAK);
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// We need to skip both the dollar and the open bracket `${`.
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env_start = &str[s_pos + 2];
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} else {
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// Toggle the normal method of accessing env variables.
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bit_set_assign(flags, ENV_NORM);
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// We need to skip the dollar `$`.
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env_start = &str[s_pos + 1];
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}
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continue;
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}
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if (bit_check(flags, ENV_BRAK)) {
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if (str[s_pos] == '}') {
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// Copy the environmental variable name.
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strncpy(buffer, env_start, &str[s_pos] - env_start);
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// Search for the environmental variable, and print it.
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if ((ENV = getenv(buffer)))
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for (int k = 0; k < strlen(ENV); ++k)
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buf[b_pos++] = ENV[k];
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// Remove the flag.
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bit_clear_assign(flags, ENV_BRAK);
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}
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continue;
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}
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if (bit_check(flags, ENV_NORM)) {
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if (str[s_pos] == ':') {
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// Copy the environmental variable name.
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strncpy(buffer, env_start, &str[s_pos] - env_start);
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// Search for the environmental variable, and print it.
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if ((ENV = getenv(buffer)))
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for (int k = 0; k < strlen(ENV); ++k)
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buf[b_pos++] = ENV[k];
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// Copy the `:`.
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buf[b_pos++] = str[s_pos];
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// Remove the flag.
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bit_clear_assign(flags, ENV_NORM);
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}
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continue;
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}
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buf[b_pos++] = str[s_pos];
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}
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if (bit_check(flags, ENV_NORM)) {
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// Copy the environmental variable name.
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strcpy(buffer, env_start);
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// Search for the environmental variable, and print it.
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if ((ENV = getenv(buffer)))
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for (int k = 0; k < strlen(ENV); ++k)
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buf[b_pos++] = ENV[k];
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// Remove the flag.
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bit_clear_assign(flags, ENV_NORM);
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}
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}
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int main(int argc, char **argv)
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{
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char buffer[BUFSIZ];
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// Iterate all the words.
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for (int i = 1; i < argc; ++i) {
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memset(buffer, 0, BUFSIZ);
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expand_env(argv[i], buffer, BUFSIZ, (i == 1), (i == (argc - 1)));
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puts(buffer);
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if (i < (argc - 1))
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putchar(' ');
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}
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printf("\n\n");
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return 0;
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}
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