There’s an xterm control sequence for this: \e]11;?\a (\e and \a are the ESC and BEL characters, respectively.) Xterm-compatible terminals should reply with the same sequence, with the question mark replaced by an X11 color name, e.g. rgb:0000/0000/0000 for black.
sed -i ‘/^$/d’ foo This tells sed to delete every line matching the regex ^$ i.e. every empty line. The -i flag edits the file in-place, if your sed doesn’t support that you can write the output to a temporary file and replace the original: sed ‘/^$/d’ foo > foo.tmp mv foo.tmp foo If you … Read more
A secure RSA encryption is implemented with an appropriate padding scheme, which includes some randomness. See PKCS#1 or OAEP for more details. The RSA encryption encrypts message padded with ‘0’s and a string of random bit. In the process, the random string is “hidden” in the ciphertext by cryptographic hashing and XORing. On decryption, the … Read more
Brace expansion, {x..y} is performed before other expansions, so you cannot use that for variable length sequences. Instead, use the seq 2 $max method as user mob stated. So, for your example it would be: max=10 for i in `seq 2 $max` do echo “$i” done
Use whole word option: grep -c -w aaa $EAT_Setup_BJ3/Log.txt From the grep manual: -w, –word-regexp Select only those lines containing matches that form whole words. The test is that the matching substring must either be at the beginning of the line, or preceded by a non-word constituent character. As noted in the comment -w is … Read more
From O’Reilly: One marked difference between the System V and POSIX semaphore implementations is that in System V you can control how much the semaphore count can be increased or decreased; whereas in POSIX, the semaphore count is increased and decreased by 1. POSIX semaphores do not allow manipulation of semaphore permissions, whereas System V … Read more
Crontab doesn’t remember what time you “started” (presumably the time you executed the crontab -e or crontab filename command). If you want to run the job every 15 minutes starting from an arbitrary time, you’ll have to specify that time. This: 7-59/15 * * * * command will run at 7, 22, 37, and 52 … Read more
dt=$(date –date yesterday “+%a %d/%m/%Y”) echo $dt
You can get as many NULL bytes as you want from /dev/zero. You can then turn these into other characters. The following prints 16 lowercase a’s head -c 16 < /dev/zero | tr ‘\0’ ‘\141’