04-29-2003
/dev/null 2>&1 question
Hi,
suppose you have the following line at your crontab :
5 * * * * /usr/mine/script > /dev/null 2>&1
now i understood that the " > /dev/null 2>&1 outputs both Standard outpout and Standard Error messages to the /dev/null device or file...
the first part , " > /dev/null " transfers the stdout messages to the /dev/null, but i am missing the part where the stderr is also dumped at dev/null.....
2(is stderr) >(send) &1 (stdout)...
i am not understanding how you send stdout first to dev/null and then send stderr to stdout which in turn will be sent to dev/null too ???
Thanks.
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LEARN ABOUT DEBIAN
stdout
FD(4) BSD Kernel Interfaces Manual FD(4)
NAME
fd, stdin, stdout, stderr -- file descriptor files
DESCRIPTION
The files /dev/fd/0 through /dev/fd/# refer to file descriptors which can be accessed through the file system. If the file descriptor is
open and the mode the file is being opened with is a subset of the mode of the existing descriptor, the call:
fd = open("/dev/fd/0", mode);
and the call:
fd = fcntl(0, F_DUPFD, 0);
are equivalent.
Opening the files /dev/stdin, /dev/stdout and /dev/stderr is equivalent to the following calls:
fd = fcntl(STDIN_FILENO, F_DUPFD, 0);
fd = fcntl(STDOUT_FILENO, F_DUPFD, 0);
fd = fcntl(STDERR_FILENO, F_DUPFD, 0);
Flags to the open(2) call other than O_RDONLY, O_WRONLY and O_RDWR are ignored.
IMPLEMENTATION NOTES
By default, /dev/fd is provided by devfs(5), which provides nodes for the first three file descriptors. Some sites may require nodes for
additional file descriptors; these can be made available by mounting fdescfs(5) on /dev/fd.
FILES
/dev/fd/#
/dev/stdin
/dev/stdout
/dev/stderr
SEE ALSO
tty(4), devfs(5), fdescfs(5)
BSD
June 9, 1993 BSD