Redirection Basics:
( < )STDIN - where to get input. i.e. keyboard, file
( > ) STDOUT - where to send processed info. i.e. Monitor, file
STDERR - where to send program error. i.e. monitor, background, file
< - STDDIN
> - STDOUT - This redirects STDOUT from screen (default) to a file
>> - STDOUT - This represents APPEND mode
< - STDIN is usually read from a keyboard (console) or file
| - PIPE - connects output of one program to input of another program
awk field processor - searches lines and tokenizes fields.
-bash-3.00$ ls -lF /etc | grep rc | awk '{ print $1,$2,$8 }'
-rw-r--r-- 1 2007
lrwxrwxrwx 1 14:15
drwxr-xr-x 2 22:23
lrwxrwxrwx 1 14:15
drwxr-xr-x 2 22:23
lrwxrwxrwx 1 14:15
drwxr-xr-x 2 12:02
lrwxrwxrwx 1 14:15
drwxr-xr-x 2 22:23
lrwxrwxrwx 1 14:15
lrwxrwxrwx 1 14:15
lrwxrwxrwx 1 14:15
drwxr-xr-x 2 22:23
drwxr-xr-x 3 14:15
drwxr-xr-x 6 14:22
-rw-r--r-- 1 09:00
-rwxr-xr-x 1 2007
-rwxr-xr-x 1 2004
STDERR
Redirection - File Descriptors:
STDIN - 0
STDOUT - 1
STDERR - 2
-bash-3.00$ ls archivo_que_no_existe
archivo_que_no_existe: No such file or directory
-bash-3.00$ echo $?
2
to instruct ls to redirect file descriptor number two to a file
-bash-3.00$ ls archivo_que_no_existe 2> error.txt
-bash-3.00$ echo $?
2
ls archivo_queno_Existe 2> error.txt - redirects STDERR to file named ‘error.txt’
/dev/null –> all is discarted
-bash-3.00$ ls archivoquenoexiste 2>/dev/null
-bash-3.00$ echo $?
2
continua….
Final de STDERR y BASHH SHELL COMMAND CHAINING
Comments are closed