Advanced Bash-shell Guide (Version 10) study notes three

The script on the book compares the more useful scripts for more records

A better way to check if the command-line arguments are numbers

e_wrongargs=85 # non-numerical argument (Bad argument format). The #42 # case "$" in43 # "") lines=50; # *[!0-9]*) echo "Usage: ' basename ' Lines-to-cleanup"; exit $E _wrongargs; # *) lines=$1;; # ESAC

Better way to check if the number of command-line arguments is correct

1 e_wrong_args=852 script_parameters= "-a-h-m-z" 3 #-A = all,-h = Help, etc.45 if [$#-ne $Number _of_expected_args]6 Then7 echo "Usage: ' basename $ ' $script _parameters" 8 # ' basename $ ' is the script ' filename.9 exit $E _wrong_args10 fi

Better way to check if the correct directory

# Cd/var/log | | {# echo "Cannot change to necessary directory." >&265 # Exit $E _xcd;66 #}

Back up the source directory files and unzip them in the target directory

(cd/source/directory && Tar CF-.) | (Cd/dest/directory && Tar xpvf-) A more efficient script is the CD source/directory# Tar CF-. | (CD..) /dest/directory; Tar xpvf-) or cp-a/source/directory/*/dest/directory# cp-a/source/directory/*/source/directory/. [^.] */dest/directory #这个复制源目录的隐藏文件

Back up files that changed over the last 24 hours

#!/bin/bashbackupfile=backup-$ (date +%m-%d-%y) archive=${1:-$BACKUPFILE}# If no parameters are specified on the command line, it is in the following format # It would default to " Backup-mm-dd-yyyy.tar.gz. " Tar cvf-' find. -mtime-1-type f-print ' > $archive. Targzip $archive. Tarecho "Directory $PWD backed up in archive file \" $archive. Tar. Gz\ "."

If the file is too many or the file name has a white-space character, the above script may be wrong

Better backup solution tar-r append to archive file

#-------------------------------------------------------------------# Find. -mtime-1-type f-print0 | Xargs-0 tar rvf "$archive. Tar" or # Find. -mtime-1-type f-exec tar rvf "$archive. Tar" ' {} ' \;exit 0

Get the last parameter of a command-line argument

args=$# # Number of args passed.lastarg=${!args}# note:this is a *indirect reference* to $args ... # or:lastarg=${!#}

${file#*/}: Take out the first/its left string: dir1/dir2/dir3/my.file.txt
${file##*/}: Take out the last/and left string: my.file.txt
${file#*.} : Take out the first one. And the string to the left: file.txt
${file##*.} : Take out the last one. And the string to the left: txt
${file%/*}: Take off the last bar/its right string:/dir1/dir2/dir3
${file%%/*}: Remove the first/its right string: (null value)
${FILE%.*}: Take off the last one. And the string to the right:/dir1/dir2/dir3/my.file
${FILE%%.*}: Take out the first one. And the string to the right:/dir1/dir2/dir3/my

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Advanced Bash-shell Guide (Version 10) study notes three