Source: Shell logical not
TL;DR
[ ! … ] is more portable than ! [ … ]
3 月 202024
11 月 112022
#!/bin/sh
retcode=0
count_retcode() {
retcode=`expr "0$retcode" + "0$?"`
}
# ......
retcode=0
apt-get -y update; count_retcode
apt-get -y install openssh-server; count_retcode
apt-get -y install apache2; count_retcode
if [ "$retcode" != "0" ]; then
echo "Failed to install required packages"
exit 1
fi11 月 112022
#!/bin/sh
help() {
echo ""
echo "My Script v1.1"
echo "Usage: $0 [OPTION] [FILE]"
echo " -b backup server"
echo " -r file restore server with the specific archive file"
echo ""
exit 1
}
while getopts "br:" opt; do
case "$opt" in
b) ACTION="BACKUP" ;;
r) ACTION="RESTORE"; RESTORE_FILE="$OPTARG" ;;
?) help ;;
esac
done
[ -z "$ACTION" ] && help11 月 072022
Source: Extract filename and extension in Bash
FILE=a.b.js
NAME=`echo "$FILE" | sed 's,\.[^\.]*$,,'`
EXTENSION=`echo "$FILE" | sed 's,.*\.,., ;t ;g'`
echo $NAME
echo $EXTENSION10 月 132017
head /dev/urandom | tr -dc A-Za-z0-9 | head -c10
9 月 102017
Source: How to create a cron job using Bash automatically without the interactive editor?
Does crontab have an argument for creating cron jobs without using the editor (crontab -e). If so, What would be the code create a cronjob from a Bash script?
6 月 082017
Source: TCP Port Scanner in Bash
I just had this quick idea to write a tcp port scanner in bash. Bash supports the special /dev/tcp/host/port file that you can read/write. Writing to this special file makes bash open a tcp connection to host:port. If writing to the port succeeds, the port is open, else the port is closed.
11 月 222016
Source: Test from shell script if remote TCP port is open
I’m looking for a quick and simple method for properly testing if a given TCP port is open on a remote server, from inside a Shell script.
I’ve managed to do it with the telnet command, and it works fine when the port is opened, but it doesn’t seem to timeout when it’s not and just hangs there…
Here’s a sample:
l_TELNET=`echo "quit" | telnet $SERVER $PORT | grep "Escape character is"`
if [ "$?" -ne 0 ]; then
echo "Connection to $SERVER on port $PORT failed"
exit 1
else
echo "Connection to $SERVER on port $PORT succeeded"
exit 0
fiI either need a better way, or a way to force telnet to timeout if it doesn’t connect in under 8 seconds for example, and return something I can catch in Shell (return code, or string in stdout).
I know of the Perl method, which uses the IO::Socket::INET module and wrote a successful script that tests a port, but would rather like to avoid using Perl if possible.
8 月 122016
Source: Doing HTTPS requests from the command line with (basic) password authentication
Imagine you want to test a web service/site secured by SSL and a password. Here is how to do that from the commandline:
7 月 172016
Source: Variables validation (name and IP address) in bash
function valid_ip()
{
ip=$1
stat=1
if echo "$ip" | egrep -E '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' >/dev/null
then
# Then the format looks right - check that each octect is less
# than or equal to 255:
VALID_IP_ADDRESS="$(echo $ip | awk -F'.' '$1 <=255 && $2 <= 255 && $3 <= 255 && $4 <= 255')"
if [ -z "$VALID_IP_ADDRESS" ]
then
#echo "The IP address wasn't valid; octets must be less than 256"
stat=1
else
#echo "The IP address was valid"
stat=0
fi
else
#echo "The IP address was malformed"
stat=1
fi
return $stat
}