Linux KILL command gives you killing opportunities to use SIGNALs. In this post we’re going to Pause (or suspend) and Start an ongoing Linux process.
Problem: The requirement here is to pause a process for certain time and run it only during off hours. The process itself doesn’t have this option and also we cannot stop it in-between, as it will start from the scratch again.
Solution: To resolve this we can think of sending out signals to the process to hint it to Pause or Progress.
A signal is an asynchronous notification sent to a process or to a specific thread within the same process in order to notify it of an event that occurred. When a signal is sent, the operating system interrupts the target process’ normal flow of execution to deliver the signal.
This post is collection of 10 useful unix / linux shell script code snippets I’ve often used.
Following these code snippet you will be able to answer following questions:
1. How to calculate script run-time in shell.
2. How to parse parameters / arguments to shell script.
3. How to safely change a directory in shell script.
4. How to check if a command was successful in shell script.
5. How to add timestamps in script log output.
6. How to check if a process is running.
7. How to colour your script output.
8. How to read variables from config file.
9. How to loop over files in a folder.
10. How to perform actions based on variable value using SWITCH…CASE
And a bonus snippet
11: How to send emails from shell script.
The Mysqldumpsplitter can extract database, table, all databases, all tables or tables matching on regular expression from a mysqldump. It can produce the compressed output of sqls in specified directories.
The tool has undergone a complete rewrite, and there are many more functionalities added. Please follow GitHub Repository for future changes or further improvements.
I have prepared a separate blog post to getting started with the mysqldumpsplitter. It’s a sort of guide for doing required and possible operations with the mysql-dump-splitter script. Read the mysqldumpsplitter recipe blog post here.
Current version is 6.1.
Watch the video of mysqldumpsplitter in action (Ver 4.0):
– I will provide more videos with latest version.
Suggestions are welcome. I’ll update it whenever time permits.
The shell script is as follows, prefer to download:
#!/bin/sh
# Current Version: 6.1
# Extracts database, table, all databases, all tables or tables matching on regular expression from the mysqldump.
# Includes output compression options.
# By: Kedar Vaijanapurkar
# Website: http://kedar.nitty-witty.com/blog
# Original Blog Post: http://kedar.nitty-witty.com/blog/mydumpsplitter-extract-tables-from-mysql-dump-shell-script
# Follow GIT: https://github.com/kedarvj/mysqldumpsplitter/
## Version Info:
# Ver. 1.0: Feb 11, 2010
# ... Initial version extract table(s) based on name, regexp or all of them from database-dump.
# Ver. 2.0: Feb, 2015
# ... Added database extract and compression
# Ver. 3.0: March, 2015
# ... Complete rewrite.
# ... Extract all databases.
# Ver. 4.0: March, 2015
# ... More validations and bug fixes.
# ... Support for config file.
# ... Detecting source dump types (compressed/sql).
# ... Support for compressed backup and bz2 format.
# Credit: Andrzej Wroblewski (andrzej.wroblewski@packetstorm.pl) for his inputs on compressed backup & bz2 support.
# Ver. 5.0: Apr, 2015
# ... Describing the dump, listing all databases and tables
# ... Extracting one or more tables from single database
# Ver. 6.1: Oct, 2015
# ... Bug fixing in REGEXP extraction functionlity
# ... Bug fixing in describe functionality
# ... Preserving time_zone & charset env settings in extracted sqls.
# Credit: @PeterTheDBA helped understanding the possible issues with environment variable settings included in first 17 lines of mysqldump.
##
# ToDo: Work with straming input
## Formating Colour
# Text color variables
txtund=$(tput sgr 0 1) # Underline
txtbld=$(tput bold) # Bold
txtred=$(tput setaf 1) # Red
txtgrn=$(tput setaf 2) # Green
txtylw=$(tput setaf 3) # Yellow
txtblu=$(tput setaf 4) # Blue
txtpur=$(tput setaf 5) # Purple
txtcyn=$(tput setaf 6) # Cyan
txtwht=$(tput setaf 7) # White
txtrst=$(tput sgr0) # Text reset
## Variable Declaration
SOURCE='';
MATCH_STR='';
EXTRACT='';
OUTPUT_DIR='out';
EXT="sql.gz";
TABLE_NAME='';
DB_NAME='';
COMPRESSION='gzip';
DECOMPRESSION='cat';
VERSION=6.1
## Usage Description
usage()
{
echo "\n\t\t\t\t\t\t\t${txtgrn}${txtund}************ Usage ************ \n"${txtrst};
echo "${txtgrn}sh mysqldumpsplitter.sh --source filename --extract [DB|TABLE|DBTABLES|ALLDBS|ALLTABLES|REGEXP] --match_str string --compression [gzip|pigz|bzip2|none] --decompression [gzip|pigz|bzip2|none] --output_dir [path to output dir] [--config /path/to/config] ${txtrst}"
echo "${txtund} ${txtrst}"
echo "OPTIONS:"
echo "${txtund} ${txtrst}"
echo " --source: mysqldump filename to process. It could be a compressed or regular file."
echo " --desc: This option will list out all databases and tables."
echo " --extract: Specify what to extract. Possible values DB, TABLE, ALLDBS, ALLTABLES, REGEXP"
echo " --match_str: Specify match string for extract command option."
echo " --compression: gzip/pigz/bzip2/none (default: gzip). Extracted file will be of this compression."
echo " --decompression: gzip/pigz/bzip2/none (default: gzip). This will be used against input file."
echo " --output_dir: path to output dir. (default: ./out/)"
echo " --config: path to config file. You may use --config option to specify the config file that includes following variables."
echo "\t\tSOURCE=
\t\tEXTRACT=
\t\tCOMPRESSION=
\t\tDECOMPRESSION=
\t\tOUTPUT_DIR=
\t\tMATCH_STR=
"
echo "${txtund} ${txtrst}"
echo "Ver. $VERSION"
exit 0;
}
## Parsing and processing input
parse_result()
{
## Validate SOURCE is provided and exists
if [ -z $SOURCE ]; then
echo "${txtred}ERROR: Source file not specified or does not exist. (Entered: $SOURCE)${txtrst}"
elif [ ! -f $SOURCE ]; then
echo "${txtred}ERROR: Source file does not exist. (Entered: $SOURCE)${txtrst}"
exit 2;
fi
## Parse Extract Operation
case $EXTRACT in
ALLDBS|ALLTABLES|DESCRIBE )
if [ "$MATCH_STR" != '' ]; then
echo "${txtylw}Ignoring option --match_string.${txtrst}"
fi;
;;
DB|TABLE|REGEXP|DBTABLE)
if [ "$MATCH_STR" = '' ]; then
echo "${txtred}ERROR: Expecting input for option --match_string.${txtrst}"
exit 1;
fi;
;;
* ) echo "${txtred}ERROR: Please specify correct option for --extract.${txtrst}"
usage;
esac;
## Parse compression
if [ "$COMPRESSION" = 'none' ]; then
COMPRESSION='cat';
EXT="sql"
echo "${txtgrn}Setting no compression.${txtrst}";
elif [ "$COMPRESSION" = 'pigz' ]; then
which $COMPRESSION &>/dev/null
if [ $? -ne 0 ]; then
echo "${txtred}WARNING:$COMPRESSION appears having issues, using default gzip.${txtrst}";
COMPRESSION="gzip";
fi;
echo "${txtgrn}Setting compression as $COMPRESSION.${txtrst}";
EXT="sql.gz"
elif [ "$COMPRESSION" = 'bzip2' ]; then
which $COMPRESSION &>/dev/null
if [ $? -ne 0 ]; then
echo "${txtred}WARNING:$COMPRESSION appears having issues, using default gzip.${txtrst}";
COMPRESSION="gzip";
fi;
echo "${txtgrn}Setting compression as $COMPRESSION.${txtrst}";
EXT="sql.bz2";
else
COMPRESSION='gzip';
echo "${txtgrn}Setting compression $COMPRESSION (default).${txtrst}";
EXT="sql.gz"
fi;
## Parse decompression
if [ "$DECOMPRESSION" = 'none' ]; then
DECOMPRESSION='cat';
echo "${txtgrn}Setting no decompression.${txtrst}";
elif [ "$DECOMPRESSION" = 'pigz' ]; then
which $DECOMPRESSION &>/dev/null
if [ $? -ne 0 ]; then
echo "${txtred}WARNING:$DECOMPRESSION appears having issues, using default gzip.${txtrst}";
DECOMPRESSION="gzip -d -c";
else
DECOMPRESSION="pigz -d -c";
fi;
echo "${txtgrn}Setting decompression as $DECOMPRESSION.${txtrst}";
elif [ "$DECOMPRESSION" = 'bzip2' ]; then
which $DECOMPRESSION &>/dev/null
if [ $? -ne 0 ]; then
echo "${txtred}WARNING:$DECOMPRESSION appears having issues, using default gzip.${txtrst}";
DECOMPRESSION="gzip -d -c";
else
DECOMPRESSION="bzip2 -d -c";
fi;
echo "${txtgrn}Setting decompression as $DECOMPRESSION.${txtrst}";
else
DECOMPRESSION="gzip -d -c";
echo "${txtgrn}Setting decompression $DECOMPRESSION (default).${txtrst}";
fi;
## Verify file type:
filecommand=`file $SOURCE`
echo $filecommand | grep "compressed" 1>/dev/null
if [ `echo $?` -eq 0 ]
then
echo "${txtylw}File $SOURCE is a compressed dump.${txtrst}"
if [ "$DECOMPRESSION" = 'cat' ]; then
echo "${txtred} The input file $SOURCE appears to be a compressed dump. \n While the decompression is set to none.\n Please specify ${txtund}--decompression [gzip|bzip2|pigz]${txtrst}${txtred} argument.${txtrst}";
exit 1;
fi;
else
echo "${txtylw}File $SOURCE is a regular dump.${txtrst}"
if [ "$DECOMPRESSION" != 'cat' ]; then
echo "${txtred} Default decompression method for source is gzip. \n The input file $SOURCE does not appear a compressed dump. \n ${txtylw}We will try using no decompression. Please consider specifying ${txtund}--decompression none${txtrst}${txtylw} argument.${txtrst}";
DECOMPRESSION='cat'; ## Auto correct decompression to none for regular files.
fi;
fi;
# Output directory
if [ "$OUTPUT_DIR" = "" ]; then
OUTPUT_DIR="out";
fi;
mkdir -p $OUTPUT_DIR
if [ $? -eq 0 ]; then
echo "${txtgrn}Setting output directory: $OUTPUT_DIR.${txtrst}";
else
echo "${txtred}ERROR:Issue while checking output directory: $OUTPUT_DIR.${txtrst}";
exit 2;
fi;
echo "${txtylw}Processing: Extract $EXTRACT $MATCH_STR from $SOURCE with compression option as $COMPRESSION and output location as $OUTPUT_DIR${txtrst}";
}
# Include first 17 lines of full mysqldump - preserve time_zone/charset/environment variables.
include_dump_info()
{
if [ $1 = "" ]; then
echo "${txtred}Couldn't find out-put file while preserving time_zone/charset settings!${txtrst}"
exit;
fi;
OUTPUT_FILE=$1
echo "Including environment settings from mysqldump."
$DECOMPRESSION $SOURCE | head -17 | $COMPRESSION > $OUTPUT_DIR/$OUTPUT_FILE.$EXT
echo "" | $COMPRESSION >> $OUTPUT_DIR/$MATCH_STR.$EXT
echo "/* -- Splitted with mysqldumpsplitter (http://goo.gl/WIWj6d) -- */" | $COMPRESSION >> $OUTPUT_DIR/$OUTPUT_FILE.$EXT
echo "" | $COMPRESSION >> $OUTPUT_DIR/$MATCH_STR.$EXT
}
## Actual dump splitting
dump_splitter()
{
case $EXTRACT in
DB)
# Include first 17 lines of standard mysqldump to preserve time_zone and charset.
include_dump_info $MATCH_STR
echo "Extracting Database: $MATCH_STR";
$DECOMPRESSION $SOURCE | sed -n "/^-- Current Database: \`$MATCH_STR\`/,/^-- Current Database: /p" | $COMPRESSION >> $OUTPUT_DIR/$MATCH_STR.$EXT
echo "${txtbld} Database $MATCH_STR extracted from $SOURCE at $OUTPUT_DIR${txtrst}"
;;
TABLE)
# Include first 17 lines of standard mysqldump to preserve time_zone and charset.
include_dump_info $MATCH_STR
#Loop for each tablename found in provided dumpfile
echo "Extracting $MATCH_STR."
#Extract table specific dump to tablename.sql
$DECOMPRESSION $SOURCE | sed -n "/^-- Table structure for table \`$MATCH_STR\`/,/^-- Table structure for table/p" | $COMPRESSION >> $OUTPUT_DIR/$MATCH_STR.$EXT
echo "${txtbld} Table $MATCH_STR extracted from $SOURCE at $OUTPUT_DIR${txtrst}"
;;
ALLDBS)
for dbname in $($DECOMPRESSION $SOURCE | grep -E "^-- Current Database: " | awk -F"\`" {'print $2'})
do
# Include first 17 lines of standard mysqldump to preserve time_zone and charset.
include_dump_info $dbname
echo "Extracting Database $dbname..."
#Extract database specific dump to database.sql.gz
$DECOMPRESSION $SOURCE | sed -n "/^-- Current Database: \`$dbname\`/,/^-- Current Database: /p" | $COMPRESSION >> $OUTPUT_DIR/$dbname.$EXT
DB_COUNT=$((DB_COUNT+1))
echo "${txtbld}Database $dbname extracted from $SOURCE at $OUTPUT_DIR/$dbname.$EXT${txtrst}"
done;
echo "${txtbld}Total $DB_COUNT databases extracted.${txtrst}"
;;
ALLTABLES)
for tablename in $($DECOMPRESSION $SOURCE | grep "Table structure for table " | awk -F"\`" {'print $2'})
do
# Include first 17 lines of standard mysqldump to preserve time_zone and charset.
include_dump_info $tablename
#Extract table specific dump to tablename.sql
$DECOMPRESSION $SOURCE | sed -n "/^-- Table structure for table \`$tablename\`/,/^-- Table structure for table/p" | $COMPRESSION >> $OUTPUT_DIR/$tablename.$EXT
TABLE_COUNT=$((TABLE_COUNT+1))
echo "${txtbld}Table $tablename extracted from $DUMP_FILE at $OUTPUT_DIR/$tablename.$EXT${txtrst}"
done;
echo "${txtbld}Total $TABLE_COUNT tables extracted.${txtrst}"
;;
REGEXP)
TABLE_COUNT=0;
for tablename in $($DECOMPRESSION $SOURCE | grep -E "Table structure for table \`$MATCH_STR" | awk -F"\`" {'print $2'})
do
# Include first 17 lines of standard mysqldump to preserve time_zone and charset.
include_dump_info $tablename
echo "Extracting $tablename..."
#Extract table specific dump to tablename.sql
$DECOMPRESSION $SOURCE | sed -n "/^-- Table structure for table \`$tablename\`/,/^-- Table structure for table/p" | $COMPRESSION >> $OUTPUT_DIR/$tablename.$EXT
echo "${txtbld}Table $tablename extracted from $DUMP_FILE at $OUTPUT_DIR/$tablename.$EXT${txtrst}"
TABLE_COUNT=$((TABLE_COUNT+1))
done;
echo "${txtbld}Total $TABLE_COUNT tables extracted.${txtrst}"
;;
DBTABLE)
MATCH_DB=`echo $MATCH_STR | awk -F "." {'print $1'}`
MATCH_TBLS=`echo $MATCH_STR | awk -F "." {'print $2'}`
if [ "$MATCH_TBLS" = "*" ]; then
MATCH_TBLS='';
fi;
TABLE_COUNT=0;
for tablename in $( $DECOMPRESSION $SOURCE | sed -n "/^-- Current Database: \`$MATCH_DB\`/,/^-- Current Database: /p" | grep -E "^-- Table structure for table \`$MATCH_TBLS" | awk -F '\`' {'print $2'} )
do
echo "Extracting $tablename..."
#Extract table specific dump to tablename.sql
# Include first 17 lines of standard mysqldump to preserve time_zone and charset.
include_dump_info $tablename
$DECOMPRESSION $SOURCE | sed -n "/^-- Current Database: \`$MATCH_DB\`/,/^-- Current Database: /p" | sed -n "/^-- Table structure for table \`$tablename\`/,/^-- Table structure for table/p" | $COMPRESSION >> $OUTPUT_DIR/$tablename.$EXT
echo "${txtbld}Table $tablename extracted from $DUMP_FILE at $OUTPUT_DIR/$tablename.$EXT${txtrst}"
TABLE_COUNT=$((TABLE_COUNT+1))
done;
echo "${txtbld}Total $TABLE_COUNT tables extracted from $MATCH_DB.${txtrst}"
;;
*) echo "Wrong option, exiting.";
usage;
exit 1;;
esac
}
missing_arg()
{
echo "${txtred}ERROR:Missing argument $1.${txtrst}"
exit 1;
}
if [ "$#" -eq 0 ]; then
usage;
exit 1;
fi
# Accepts Parameters
while [ "$1" != "" ]; do
case $1 in
--source|-S ) shift
if [ -z $1 ]; then
missing_arg --source
fi;
SOURCE=$1 ;;
--extract|-E ) shift
if [ -z $1 ]; then
missing_arg --extract
fi;
EXTRACT=$1 ;;
--compression|-C ) shift
if [ -z $1 ]; then
missing_arg --compression
fi;
COMPRESSION=$1 ;;
--decompression|-D) shift
if [ -z $1 ]; then
missing_arg --decompression
fi;
DECOMPRESSION=$1 ;;
--output_dir|-O ) shift
if [ -z $1 ]; then
missing_arg --output_dir
fi;
OUTPUT_DIR=$1 ;;
--match_str|-M ) shift
if [ -z $1 ]; then
missing_arg --match_str
fi;
MATCH_STR=$1 ;;
--desc )
EXTRACT="DESCRIBE"
parse_result
echo "-------------------------------";
echo "Database\t\tTables";
echo "-------------------------------";
$DECOMPRESSION $SOURCE | grep -E "(^-- Current Database:|^-- Table structure for table)" | sed 's/-- Current Database: /-------------------------------\n/' | sed 's/-- Table structure for table /\t\t/'| sed 's/`//g' ;
echo "-------------------------------";
exit 0;
;;
--config ) shift;
if [ -z $1 ]; then
missing_arg --config
fi;
if [ ! -f $1 ]; then
echo "${txtred}ERROR: Config file $1 does not exist.${txtrst}"
exit 2;
fi;
. ./$1 ;;
-h ) usage
exit ;;
* ) echo "";
usage
exit 1
esac
shift
done
parse_result
dump_splitter
exit 0;
MySQL Dump Splitter Version Info:
Version-1: Initial script (Feb-11, 2010)
Version-2: (Feb,2015)
– The script is updated to generate compressed output of sqls.
– Script can be used to extract a database.
Version-3: (March-2, 2015)
– Complete rewrite of the script
– Script can extract all databases.
Version-4: (March-15, 2015)
– More validations and bug fixes.
– Detecting source dump types (compressed/sql).
– Support for compressed backup and bz2 format.
– Support for config file.
Version-5: (April-25, 2015)
– Describing the dump, listing all databases and tables
– Extracting one or more tables from single database
Version-6.1: Oct, 2015
– Bug fixing in REGEXP extraction functionality
– Bug fixing in describe functionality
– Preserving time_zone & charset env settings in extracted sqls.
Old Version (very first) of mysqldumpsplitter is available for download.
This article explain a way to get a mail as soon as the disk usage reaches to its critical level to avoid issues later. To set a simple monitor on Linux / Unix, I have two simple scripts:
DSAlert.sh : Shell script for retrieving disk space percentages and put in to a cron job.
DiskSpace_Alert.pl : Perl script for sending an email.
Following is the disk monitor shell script which will execute the perl file for sending alert email.
#DSAlert.sh
#!/bin/sh
#Retrive disk space info
df=`df -Pl | grep "^/dev" | awk '{print $5, $6}' | sed "s/%//"`
#Reference: df
echo “$df” | while read percent fs
do
#If Disk Usage increases above 90% send an email.
if [ $percent -ge 90 ] ; then
#Calling a perl file with parameters for sending an email.
`/opt/lampp/bin/perl DiskSpace_Alert.pl $fs is $percent percent full`
fi
done
# set up email
$to = “my-mail-id\@domain.com”;
$from = “Diskmonitor\@ServerName.com”;
$subject = “Disk_Alert”;
$message = “Disk Space issue.\nActions Required:\n”.”@ARGV”;
# send email
email($to, $from, $subject, $message, $file);
# email function
sub email
{
# get incoming parameters
local ($to, $from, $subject, $message, $file) = @_;
# create a new message
$msg = MIME::Lite->new(
From => $from,
To => $to,
Subject => $subject,
Data => $message);
# send the email
