Hi, with grep 3.3 I see for a FIFO this
echo XXX | strace grep -E XXX
[...]
fstat(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(0x88, 0xc), ...}) = 0
stat("/dev/null", {st_mode=S_IFCHR|0666, st_rdev=makedev(0x1, 0x3), ...}) = 0
fstat(0, {st_mode=S_IFIFO|0600, st_size=0, ...}) = 0
lseek(0, 0, SEEK_CUR) = -1 ESPIPE (Illegal seek)
read(0, "XXX\n", 98304) = 4
fstat(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(0x88, 0xc), ...}) = 0
write(1, "XXX\n", 4XXX) = 4
read(0, "", 98304) = 0
close(1) = 0
close(2) = 0
exit_group(0) = ?
+++ exited with 0 +++
prefect but with libpipeline configured to use much faster socketpairs I see
this:
strace -f ./mgrep -e XXX
clone(strace: Process 2020 attached
child_stack=NULL, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD,
child_tidptr=0x7fb632fb4a10) = 2020
[...]
[pid 2020] execve("/usr/bin/grep", ["grep", "-e XXX"], 0x7ffd31f42ea8 /* 128
vars */ <unfinished ...>
[...]
[pid 2020] fstat(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(0x88, 0xc), ...})
= 0
[pid 2020] stat("/dev/null", {st_mode=S_IFCHR|0666, st_rdev=makedev(0x1,
0x3), ...}) = 0
[pid 2020] fstat(0, {st_mode=S_IFSOCK|0400, st_size=0, ...}) = 0
[pid 2020] lseek(0, 0, SEEK_CUR) = -1 ESPIPE (Illegal seek)
[pid 2020] read(0, "XXX\n", 98304) = 4
[pid 2020] read(0, "", 98304) = 0
[pid 2020] close(1) = 0
[pid 2020] close(2) = 0
[pid 2020] exit_group(1) = ?
[pid 2020] +++ exited with 1 +++
IMHO reading data from a FIFO/pipe or from a FSOCK/socket(pair) should result
in the same result. The mgrep is a simple test C code which uses libpipeline
to write "XXX\n" to a FILE stream used on the input fd of the sub process for
the grep command:
FILE *xy;
int fd = dup(1);
pipeline *p = pipeline_new();
pipeline_want_in(p, -1);
pipeline_want_out(p, fd);
pipecmd *grep = pipecmd_new("/usr/bin/grep");
[... handle options and arguments ...]
xy = pipeline_get_infile (p);
fprintf(xy, "XXX\n");
fflush(xy);
fclose(xy);
Nevertheless in both cases stdout for grep is 136/12 aka /dev/pts/12
Werner
--
"Having a smoking section in a restaurant is like having
a peeing section in a swimming pool." -- Edward Burr
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