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copy-file now truncates output after writing

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* src/fileio.c (Fcopy_file): Truncate output after writing rather
than before.  This is more likely to work than truncation before
writing, if the file system is out of space or the user is over
disk quota (Bug#20595).  Also, check for read errors.
This commit is contained in:
Paul Eggert 2015-05-29 22:55:25 -07:00
parent 56af96e54e
commit 2c3dde9fc8
1 changed files with 23 additions and 7 deletions
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30
src/fileio.c
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@ -1871,8 +1871,6 @@ permissions. */)
bool already_exists = false;
mode_t new_mask;
int ifd, ofd;
int n;
char buf[16 * 1024];
struct stat st;
#endif
@ -1974,6 +1972,8 @@ permissions. */)
record_unwind_protect_int (close_file_unwind, ofd);
off_t oldsize = 0, newsize = 0;
if (already_exists)
{
struct stat out_st;
@ -1982,15 +1982,31 @@ permissions. */)
if (st.st_dev == out_st.st_dev && st.st_ino == out_st.st_ino)
report_file_errno ("Input and output files are the same",
list2 (file, newname), 0);
if (ftruncate (ofd, 0) != 0)
report_file_error ("Truncating output file", newname);
if (S_ISREG (out_st.st_mode))
oldsize = out_st.st_size;
}
immediate_quit = 1;
QUIT;
while ((n = emacs_read (ifd, buf, sizeof buf)) > 0)
if (emacs_write_sig (ofd, buf, n) != n)
report_file_error ("Write error", newname);
while (true)
{
char buf[MAX_ALLOCA];
ptrdiff_t n = emacs_read (ifd, buf, sizeof buf);
if (n < 0)
report_file_error ("Read error", file);
if (n == 0)
break;
if (emacs_write_sig (ofd, buf, n) != n)
report_file_error ("Write error", newname);
newsize += n;
}
/* Truncate any existing output file after writing the data. This
is more likely to work than truncation before writing, if the
file system is out of space or the user is over disk quota. */
if (newsize < oldsize && ftruncate (ofd, newsize) != 0)
report_file_error ("Truncating output file", newname);
immediate_quit = 0;
#ifndef MSDOS