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system/dd: Implement conv=notrunc

Browse source 
https://pubs.opengroup.org/onlinepubs/9699919799/utilities/dd.html
> notrunc
>   Do not truncate the output file. Preserve blocks in the output
>   file not explicitly written by this invocation of the dd utility.

Signed-off-by: YAMAMOTO Takashi <yamamoto@midokura.com>
This commit is contained in:
YAMAMOTO Takashi 2025-04-02 22:58:58 +09:00 • committed by Xiang Xiao
parent 5d4b720596
commit 61551aa849
1 changed files with 29 additions and 1 deletions
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30
system/dd/dd_main.c
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@ -79,6 +79,7 @@ struct dd_s
uint32_t skip; /* The number of sectors skipped on input */
uint32_t seek; /* The number of sectors seeked on output */
bool eof; /* true: The end of the input or output file has been hit */
bool notrunc; /* conv=notrunc */
uint16_t sectsize; /* Size of one sector */
uint16_t nbytes; /* Number of valid bytes in the buffer */
FAR uint8_t *buffer; /* Buffer of data to write to the output file */
@ -186,7 +187,8 @@ static inline int dd_outfopen(FAR const char *name, FAR struct dd_s *dd)
return OK;
}
dd->outfd = open(name, O_WRONLY | O_CREAT | O_TRUNC, 0644);
dd->outfd = open(name, O_WRONLY | O_CREAT | (dd->notrunc ? 0 : O_TRUNC),
0644);
if (dd->outfd < 0)
{
fprintf(stderr, "%s: failed to open '%s': %s\n",
@ -259,6 +261,32 @@ int main(int argc, FAR char **argv)
{
dd.seek = atoi(&argv[i][5]);
}
else if (strncmp(argv[i], "conv=", 5) == 0)
{
const char *cur = &argv[i][5];
while (true)
{
const char *next = strchr(cur, ',');
size_t len = next != NULL ? next - cur : strlen(cur);
if (len == 7 && !memcmp(cur, "notrunc", 7))
{
dd.notrunc = true;
}
else
{
fprintf(stderr, "%s: unknown conversion '%.*s'\n", g_dd,
(int)len, cur);
goto errout_with_paths;
}
if (next == NULL)
{
break;
}
cur = next + 1;
}
}
else
{
print_usage();