Linux shell-Common scripts

1. Determine the logged-on user

1.1 Scripts

[Email protected]_1 shell]$ VI check_user.sh#! /bin/shecho "You is logged in as ' WhoAmI '"; if [' whoami '! = Devtac]; Then  echo "must is logged in as Devtac-to-run this script."  Exitfiecho "Running script at ' Date '"

1.2 Running results

[Email protected]_1 shell]$ chmod a+x check_user.sh [[Email protected]_1 shell]$./check_user.sh you is logged in as Dev tacrunning script at December 09, 2014 Tuesday 13:35:17 CST

2. Determine whether to continue execution

2.1 Scripts

[Email protected]_1 shell]$ VI do_continue.sh#! /bin/shdocontinue=necho really want to continue? (y/n) "Read Docontinueif [" $doContinue "! = y]; Then   echo "quitting ..."   Exitfiecho "OK ... we'll continue."

2.2 Running Results

3 Hidden input

3.1 Scripts

[Email protected]_1 shell]$ VI hide_input.sh#! /bin/shstty-echoecho-n "Enter The database system password:" Read Pwstty Echoecho "$PW was entered"

3.2 Results

3.3 Parsing

Stty command

3.3.1 Man Manual definition

DESCRIPTION       Print or change terminal characteristics.

[Email protected]_1 shell]$ stty-aspeed 38400 baud; Rows 47; Columns 125; line = 0;intr = ^c; Quit = ^\; erase = ^?; Kill = ^u; EOF = ^d; EOL = <undef>; Eol2 = <undef>; Swtch = <undef>; start = ^q; stop = ^s;susp = ^z; Rprnt = ^r; Werase = ^w; Lnext = ^v; flush = ^o; min = 1; Time = 0;-parenb-parodd CS8-HUPCL-CSTOPB Cread-clocal-crtscts-cdtrdsr-ignbrk-brkint-ignpar-parmrk-inpck-istrip -INLCR-IGNCR icrnl ixon-ixoff-iuclc-ixany-imaxbel-iutf8opost-olcuc-ocrnl Onlcr-onocr-onlret-ofill-ofdel nl0 cr 0 tab0 bs0 vt0 ff0isig icanon iexten echo echoe echok-echonl-noflsh-xcase-tostop-echoprt echoctl Echoke

The parameters used in this example

       [-]echo              echo Input characters

Shielding display
Stty-echo #禁止回显
Stty Echo #打开回显
Test method:
Stty-echo;read;stty Echo;read

Summary: The effect of using Stty-echo is like when we enter a Linux login password, we don't see the input

4 Deciding whether to catalog

4.1 Scripts

[Email protected]_1 shell]$ VI is_a_directory.sh #! /bin/shif [-Z "$"]; Then echo "echo" error:invalid number of   arguments "   echo" Usage: $ arg1 "   echo" "   Exitfiif [-D $ 1]; Then   Echo, "is a directory." Else   echo "is not a directory." Fi

4.2 Test Results

[Email protected]_1 shell]$/is_a_directory.sh error:invalid number of argumentsusage:./is_a_directory.sh Arg1[[emai L protected]_1 shell]$./is_a_directory.sh $PWD/home/devtac/shell is a directory.

4.3 parsing

4.3.1 Script Pass (not all tested, for reference only)

$ A script name
Location parameter #1
$-$9 positional parameter #2-#9
${10} positional Parameters #10
$# Number of positional parameters
"$*" all positional parameters (as a single string) *
"[Email protected]" All positional parameters (each as a separate string)
${#*} The number of command-line arguments passed to the script
${#@} The number of command-line arguments passed to the script
$? return value
Process ID (PID) of the $$ script
$-the flags passed to the script (using set)
$_ the last parameter of the previous command
$! Process ID (PID) of the last job running in the background

4.3.2 to determine if the parameter is empty, to interpret whether the directory exists

-Z String
True if the length of string is zero.

-D Directory

True if the directory exists.

5. Interpretation of the document is readable

5.1 Scripts

[Email protected]_1 shell]$ VI is_readable.sh#! /bin/shif [-Z "$"]; Then echo "echo" error:invalid number of   arguments "   echo" Usage: $ AGR1 "   echo" "   exitfiif [! -R $]; Then   echo "are not readable." Else   echo "is readable." fi~

5.2 Test Results

[Email protected]_1 shell]$/is_readable.sh error:invalid number of argumentsusage:./is_readable.sh agr1[[email Prot Ected]_1 shell]$./is_readable.sh Asdfasasdfas is not readable. [Email protected]_1 shell]$/is_readable.sh $PWD/home/devtac/shell is readable. [Email protected]_1 shell]$/is_readable.sh/home/devtac//home/devtac/is readable. [Email protected]_1 shell]$./is_readable.sh/home/devtac/shell/is_readable.sh/home/devtac/shell/is_readable.sh is Readable.

6 Output Script Parameters

6.1 Scripts

[Email protected]_1 shell]$ VI print_args.sh#! /bin/shwhile [$#-ne 0]   do      echo $      shift   Done

6.2 Output Results

6.3 Parsing

6.3.1 Shift Command

For positional variables or command-line arguments, the number must be deterministic, or when the shell program does not know its number, you can assign all parameters together to the variable $*. If the user requires that the shell do not know the number of positional variables, but also one by one to the parameter one by one processing, that is, after $ $, after the $ $ $, and so on. The value of the variable before the shift command executes is not available after the shift command executes.

7 Copy directory files to a directory

7.1 Scripts

[Email protected]_1 shelltemp2]$ VI copy_special_dir_file.sh

#! /bin/sh

#echo $#
# If the number of the args is not equal 2, output command usage and exit
If [$#-ne 2];then
echo "Usage: $ fromdir Todir"
Exit 1
Fi

Fromdir=$1 #from Directory
Todir=$2 #to Directory
#echo $fromdir $todir

#if Fromdir or Todir is not a valid directory, exit
if [!-D $fromdir] | | [!-D $todir];then
echo $fromdir or $todir is not a valid directory
Exit 1
Fi

For i in $fromdir/*; Do
If [-f $i]; Then
filename=${i# $fromdir/}
echo copying $i to $todir/$filename
Cp-p $i $todir/$filename
Fi
Done
Exit 0

7.2 Test Results

[[Email protected]_1 shell]$./copy_special_dir_file.sh/home/devtac/shell/home/devtac/shelltemp2/qewqe/home /devtac/shell OR/HOME/DEVTAC/SHELLTEMP2/QEWQE is not a valid Directory[[email protected]_1 shell]$ rm. /shelltemp2/*[[email protected]_1 shell]$./copy_special_dir_file.sh/home/devtac/shell/home/devtac/ Shelltemp2copying/home/devtac/shell/a.txt To/home/devtac/shelltemp2/a.txtcopying/home/devtac/shell/b.txt To/home /devtac/shelltemp2/b.txtcopying/home/devtac/shell/check_user.sh to/home/devtac/shelltemp2/check_user.shcopying/ Home/devtac/shell/copy_special_dir_file.sh to/home/devtac/shelltemp2/copy_special_dir_file.shcopying/home/ DEVTAC/SHELL/COPY_SPECIAL_DIR_FILE.SH.BK to/home/devtac/shelltemp2/copy_special_dir_file.sh.bkcopying/home/ Devtac/shell/do_continue.sh to/home/devtac/shelltemp2/do_continue.shcopying/home/devtac/shell/hide_input.sh to/ Home/devtac/shelltemp2/hide_input.shcopying/home/devtac/shell/is_a_directory.sh to/home/devtac/shelltemp2/iS_a_directory.shcopying/home/devtac/shell/is_readable.sh to/home/devtac/shelltemp2/is_readable.shcopying/home/ devtac/shell/print_args.sh to/home/devtac/shelltemp2/print_args.shcopying/home/devtac/shell/sh01.sh to/home/  Devtac/shelltemp2/sh01.sh[[email protected]_1 shell]$

7.3 Parsing

7.3.1filename=${i# $fromdir/}

Hypothesis: I=/home/devtac/shell/a.txt

Fromdir=/home/devtac/shell/a.txt

Then: Filename=a.txt

Reference: Source http://linux.chinaunix.net/techdoc/develop/2007/05/05/956956.shtml

For the sake of completeness, I'll use some examples here to illustrate some of the supernatural powers of ${}:
Suppose we define a variable as:
File=/dir1/dir2/dir3/my.file.txt
We can replace each other with ${} to get different values:
${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
The methods of memory are:

# is to remove the left side (on the plate # on the left of the $)

% is removed to the right (on the plate% on the right of the $)

The
single symbol is the minimum match, and the two symbol is the maximum match.

${file:0:5}: Extract the leftmost 5 bytes:/dir1
${file:5:5}: Extracts the 5th byte to the right of 5 consecutive bytes:/DIR2
We can also replace the string in the value of the variable:
${file/dir/path}: Change the first dir to Path:/path1/dir2/dir3/my.file.txt
${file//dir/path}: Change all dir to path:/path1/path2/path3/my

Network reference:

Http://www.ha97.com/4020.html

http://blog.csdn.net/tianlesoftware/article/details/5381984

http://blog.csdn.net/qzwujiaying/article/details/6371246

Http://linux.chinaunix.net/techdoc/develop/2007/05/05/956956.shtml

Books:

Http://www.comptechdoc.org/os/linux/usersguide/linux_ugshellpro.html

Linux shell-common scripts