Shell modified file name (a)

If the file name is: Time_filename.txt changed to Filename_time.txt. For example 20111111_me.txt change to me_201111111.txt how to modify?

1#! /bin/SH2  forEachfileinch`ls-B '3  Do4Filename=${eachfile%. txt}5Filehead= 'Echo$filename |awk-F _'{print $}'`6Filelast= 'Echo$filename |awk-F _'{print $}'`7  MV$filename. txt ${filelast}_$filehead.txt8  Done

Description

The default file you want to work with is in a folder with the suffix txt:
The 2nd line is to list all the files, and then 4-7 lines of processing for each file;
The 4th line is to get the file name, not including the suffix txt;
Then the filename is divided into two parts: Filehead and Filelast;
Finally, rename the source file to Filelast_filehead.txt.

Add:

${},# #和 percent usage in the shell

Suppose we define a variable as:
File=/dir1/dir2/dir3/my.file.txt

Different values can be replaced with ${}, respectively:

1. Truncation function
${file#*/}: Remove the first one/And the string to its left:Dir1/dir2/dir3/my.file.txt
${file##*/}: Erase the last one/And the string to its left:My.file.txt
${file#*.}: Remove the first one.And the string to its left:File.txt
${file##*.}: Erase the last one.And the string to its left:Txt
${file%/*}: Erase the last one//dir1/dir2/dir3
${file%%/*}: Delete the first null value Span style= "color: #333333;" >)
${file%.*}: Erase the last one.  .   and its right string: /dir1/dir2/dir3/my.file
${file%%.*}: Delete the first  .   and its right string: /dir1/dir2/dir3/my

Memory by:
#是去掉左边 (on keyboard # on the left of $), # #最后一个;
% is remove right (on keyboard% in $ to the right), and the first one.
/span>

< Span style= "color: #333333;" >< Span style= "color: #333333;" >< Span style= "color: #333333;" >2. String Extraction

< Span style= "color: #333333;" > single A symbol is the minimum match; two symbols are the maximum match
${file:0:5}: Extract the leftmost 5 bytes: /dir1
${file:5:5} : Extract the 55 bytes: /dir2

3. String substitution

You can also replace the string in the value of the variable:
: The first dir Replace with path:/path1/dir2/dir3/my.file.txt
${file//dir/ Path}dir Path:/path1/path2/path3/my.file.txt
/span>

< Span style= "color: #333333; Background:white; " > 4. < Span style= "color: #333333;" > assign values for different variable states (no setting, null value, non-null value):
${file-my.file.txt}: If the $file is not set, use My.file.txt as the return value. (null and non-null values are not processed)
${file:-my.file.txt}: If $file is not set or null, use My.file.txt as the return value. (Non-null value is not processed)
${file+my.file.txt}: Use My.file.txt as the return value if $file is set to a null or non-null value. (not processed when not set)
${file:+my.file.txt}: If $file is a non-null value, use My.file.txt as the return value. (No processing when not set and null value)
${file=my.file.txt}: If $file is not set, My.file.txt is used as the return value, and $file is assigned my.file.txt. (null and non-null values are not processed)
${file:=my.file.txt}: If $file is not set or null, use My.file.txt as the return value and assign the $file to My.file.txt. (Non-null value is not processed)
${file?my.file.txt}: If $file is not set, output my.file.txt to STDERR. (null and non-null values are not processed)
${file:?my.file.txt}: If $file is not set or null, the my.file.txt output to stderr. (Non-null value is not processed)

${#var}
${# File} can get 27 because /dir1/dir2/dir3/my.file.txt 27 bytes.

Note:
The ": +" case does not contain a null value.
":-", ": =" as long as there is a number is a null value (NULL).

5. Length of the variable
${#file}

6. Array operations
A= (a b c def)
${a[@]} or ${a[*]} to get A b C def (total number of groups)
${a[0]} can get a (number of first group), ${a[1]} is the second group number ...
${#A [@]} or ${#A [*]} to get 4 (total number of groups)
${#A [0]} can get 1 (that is, the length of the first group (a), ${#A [3]} can get 3 (fourth group number (def) length)

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Shell modified file name (a)