Re: [PATCH 1/1] command: add read command

[Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>]

On 10:15 Fri 27 Sep     , Sascha Hauer wrote:
> On Thu, Sep 26, 2013 at 07:45:56AM +0200, Jean-Christophe PLAGNIOL-VILLARD wrote:
> > +static int do_read(int argc, char *argv[])
> > +{
> > +	int opt;
> > +	int cont = 0;
> > +	int ret = -EINVAL;
> > +	char *var;
> > +	char *buf = xzalloc(2049);
> > +	char *filename = NULL;
> > +
> > +	if (!argc)
> > +		return COMMAND_ERROR_USAGE;
> > +
> > +	while((opt = getopt(argc, argv, "cf:")) > 0) {
> > +		switch(opt) {
> > +		case 'c':
> > +			cont = 1;
> > +			break;
> 
> Do you really need this continue mode? It makes this stuff look rather
> flawy. For example one must know that this command is not reentrant. Not
> that it's likely that someone parses a file while parsing another file,
> but doing so would lead to strange results and is hard to fix.
> 
> BTW I had to do very similar stuff recently, see attached what I came up
> with.

I agree on the issue but as we do not have the | on the shell and I do need to
read multiple  line on a project. SO the only way would be to use a list of
open files

Best Regards,
J.
> 
> Sascha
> 
> 
> From 5d513270e46c5705262d79c66cc630e20d1a66d9 Mon Sep 17 00:00:00 2001
> From: Sascha Hauer <s.hauer@pengutronix.de>
> Date: Sun, 22 Sep 2013 23:40:04 +0200
> Subject: [PATCH] add function to read single line files
> 
> Often small files are used to store the value of a variable. This
> adds a function to easily read such a variable.
> 
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
>  include/libbb.h |  2 ++
>  lib/libbb.c     | 42 ++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 44 insertions(+)
> 
> diff --git a/include/libbb.h b/include/libbb.h
> index 47b2e08..2fe710c 100644
> --- a/include/libbb.h
> +++ b/include/libbb.h
> @@ -35,4 +35,6 @@ char *simple_itoa(unsigned int i);
>  int write_full(int fd, void *buf, size_t size);
>  int read_full(int fd, void *buf, size_t size);
>  
> +char *read_file_line(const char *fmt, ...);
> +
>  #endif /* __LIBBB_H */
> diff --git a/lib/libbb.c b/lib/libbb.c
> index e0d7481..200629e 100644
> --- a/lib/libbb.c
> +++ b/lib/libbb.c
> @@ -176,3 +176,45 @@ int read_full(int fd, void *buf, size_t size)
>  	return insize;
>  }
>  EXPORT_SYMBOL(read_full);
> +
> +/*
> + * read_file_line - read a line from a file
> + *
> + * Used to compose a filename from a printf format and to read a line from this
> + * file. All leading and trailing whitespaces (including line endings) are
> + * removed. The returned buffer must be freed with free(). This function is
> + * supposed for reading variable like content into a buffer, so files > 1024
> + * bytes are ignored.
> + */
> +char *read_file_line(const char *fmt, ...)
> +{
> +	va_list args;
> +	char *filename;
> +	char *buf, *line = NULL;
> +	int size, ret;
> +	struct stat s;
> +
> +	va_start(args, fmt);
> +	filename = asprintf(fmt, args);
> +	va_end(args);
> +
> +	ret = stat(filename, &s);
> +	if (ret)
> +		goto out;
> +
> +	if (s.st_size > 1024)
> +		goto out;
> +
> +	buf = read_file(filename, &size);
> +	if (!buf)
> +		goto out;
> +
> +	line = strim(buf);
> +
> +	line = xstrdup(line);
> +	free(buf);
> +out:
> +	free(filename);
> +	return line;
> +}
> +EXPORT_SYMBOL_GPL(read_file_line);
> -- 
> 1.8.4.rc3
> 
> -- 
> Pengutronix e.K.                           |                             |
> Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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