Description | Command | Example |
---|---|---|
How to get date in YYYYMMDDhhmmss format
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date +%Y%m%d%H%M%S | date +%Y%m%d%H%M%S 20150701164849 |
How to get hostname | uname -n | |
How to unzip and untar a file | gunzip -c filename | tar -xvf - | |
How to check if a file is non zero size | if [ -s file ] | |
How to check if a variable is empty | if [ -z file] | |
How to check if a directory is present | if [ -d file] | |
How to check if a file is present | if [ -f file] | |
How to extract file name from path | echo filename | sed -e's/.*\///' | # echo "/opt/app/tmp/pom.xml" | sed -e's/.*\///' pom.xml |
How to zip a file | cat $file | gzip -c > $FILENAME | |
How to retrieve return status from a shell | $CTI/common/shells/SendToETL.sh TOPO $FILENAME RC=$? echo "Return status = $RC" |
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How to run a command on a remote server | ssh -l user hostname '. ./.profile;echo $JAVA_HOME' | ssh -l jm416b abc.com '. ./.profile;echo $JAVA_HOME' |
How to view contents of a zip file | zcat file.gz | |
How to retrieve result to an integer variable | integer RESULT=$(wc -l $DIFFFILE | cut -d' ' -f1) | |
Numeric comparison | if [ $RESULT -gt 0 ] | you can also use -gt,-ge,-le,-lt,-eq,-ne |
String comparison | if [ "$HLCS" != "" ] | use = = for equality |
Convert uppercase to lowercase | DNS=$(echo "$DNS" | tr '[A-Z]' '[a-z]' | |
Convert lowercase to uppercase | DNS=$(echo "$DNS" | tr '[a-z]' '[A-Z]' | |
A file is newer than another | if [[ FILE1 -nt FILE2 ]]; then
echo FILE1 is newer than FILE2 fi |
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A file is older than another | if [[ FILE1 -nt FILE2 ]]; then echo FILE1 is newer than FILE2 fi |
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You can follow these steps to install a mac OS on an old Mac book following these steps. Here I assume that you have the actual bootable CD for the OS for installation. 1. Restart the laptop 2. Press Command + R key until it shows recovery mode 3. Open Disk Utilities 4. Select the hard drive and try to partition the drive. For example I have created a partition called Partition1 5. Insert bootable CD and restart the laptop. When option comes choose to boot from the CD. 6. Choose partition1 as the place to install the OS 7. Continue the installation process. 8. Once installation is completed then it might need to restart for further updates. 9. Most of the times a more recent compatible version of the OS might be available. In order to upgrade to the more latest compatible OS follow below steps. 11. Find the latest compatible version of OS. 12. Go to apple support sites and manually download the image and click to install. 13. Follow installation instructions and this would upgrade you
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