Update a configuration file: Difference between revisions

=={{header|C}}==

C with POSIX <code>strcasecmp</code> function for case-insensitive comparing. Substitute your toolchain's version.

<lang C>#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#define strcomp(X, Y) strcasecmp(X, Y)

struct option

{ char *name, *value;

int flag; };

/* TODO: dynamically obtain these */

struct option updlist[] =

{ { "NEEDSPEELING", NULL },

{ "SEEDSREMOVED", "" },

{ "NUMBEROFBANANAS", "1024" },

{ "NUMBEROFSTRAWBERRIES", "62000" },

{ NULL, NULL } };

int output_opt(FILE *to, struct option *opt)

{ if (opt->value == NULL)

return fprintf(to, "; %s\n", opt->name);

else if (opt->value[0] == 0)

return fprintf(to, "%s\n", opt->name);

else

return fprintf(to, "%s %s\n", opt->name, opt->value); }

int update(FILE *from, FILE *to, struct option *updlist)

{ char line_buf[256], opt_name[128];

int i;

for (;;)

{ size_t len, space_span, span_to_hash;

if (fgets(line_buf, sizeof line_buf, from) == NULL)

break;

len = strlen(line_buf);

space_span = strspn(line_buf, "\t ");

span_to_hash = strcspn(line_buf, "#");

if (space_span == span_to_hash)

goto line_out;

if (space_span == len)

goto line_out;

if ((sscanf(line_buf, "; %127s", opt_name) == 1) ||

(sscanf(line_buf, "%127s", opt_name) == 1))

{ int flag = 0;

for (i = 0; updlist[i].name; i++)

{ if (strcomp(updlist[i].name, opt_name) == 0)

{ if (output_opt(to, &updlist[i]) < 0)

return -1;

updlist[i].flag = 1;

flag = 1; } }

if (flag == 0)

goto line_out; }

else

line_out:

if (fprintf(to, "%s", line_buf) < 0)

return -1;

continue; }

{ for (i = 0; updlist[i].name; i++)

{ if (!updlist[i].flag)

if (output_opt(to, &updlist[i]) < 0)

return -1; }}

return feof(from) ? 0 : -1; }

int main(void)

{ if (update(stdin, stdout, updlist) < 0)

{ fprintf(stderr, "failed\n");

return (EXIT_FAILURE); }

return 0; }</lang>

Run:

<pre>$ ./a.out < configfile

# This is a configuration file in standard configuration file format

#

# Lines begininning with a hash or a semicolon are ignored by the application

# program. Blank lines are also ignored by the application program.

# The first word on each non comment line is the configuration option.

# Remaining words or numbers on the line are configuration parameter

# data fields.

# Note that configuration option names are not case sensitive. However,

# configuration parameter data is case sensitive and the lettercase must

# be preserved.

# This is a favourite fruit

FAVOURITEFRUIT banana

# This is a boolean that should be set

; NEEDSPEELING

# This boolean is commented out

SEEDSREMOVED

# How many bananas we have

NUMBEROFBANANAS 1024

NUMBEROFSTRAWBERRIES 62000</pre>