[Linux] structured command-for

1 for command

1  for : iteration loop; default space is delimiter 2 3  for var inch List 4  Do 5     Commands6 Done

1.1 reading the values in the list

#!usr/bin/bash for in Hello Python Student School    does is is $test # keeps the value of the last iteration until it is deleted (or changed)  

1.2 Reading complex values in a list

 1  # use escape character (backslash), escape special character  2  # use double quotation marks to define the single quotation mark (or vice versa)  3  # Default space is delimiter 4  #!usr/bin/bash  5  for  test in  I don\ " t know if" This  "  ll "  work  6  do  7  Echo Span style= "COLOR: #800000" > " word: $test  "  8  done 

# double quotes Create a string variable and appear as a whole in the list $cat fortest01.sh#!usr/bin/Bash for var inch "The Test bash Shell" Doecho Word: $vardone$sh fortest01.shword:the Test bash Shell$cat fortest01.sh#!usr/bin/Bash for var inch "The Test bash Shell" "The last test" Doecho Word: $vardone$sh fortest01.shword:the Test bash shellword:the last Test

1.3 Reading a list from a variable

1 # Note the difference from the direct read list:2 # list:3*escape characters for special characters in the list4* Double Quotes-special characters and string variables (overall)5 # variable6* Define string variables-double quotes/single quotation marks7*string add element8*For Iteration traversal variable element9 $cat varfortest02.shTen#!usr/bin/Bash Onelist01='The first test example' AList02="The Second Test example" -list03= $list 02"The thrid Test Example" -list04=$list 01$list02$list03 the Echo $list -n=0 -  for var inch$list -  Do +((n++ )) -Echo Cycle $n: $var +  Done A  at $sh varfortest02.sh - The first test example the second Test example the second Test example the Thrid test example -Cycle1: the -Cycle2: First -Cycle3: Test -Cycle4: Example inCycle5: the -Cycle6: Second toCycle7: Test +Cycle8: Example -Cycle9: the theCycleTen: Second *Cycle One: Test $Cycle A: ExamplePanax NotoginsengCycle -: the -Cycle -: Thrid theCycle the: Test +Cycle -: Example

1.4 reading a value from a command

1 # anti-quote2*use the absolute path of the file, unless you are in the same directory3*default space is delimiter4 $cat commandfor.sh5#!usr/bin/Bash6n=07  for var inch' Cat varfortest02.sh '8  Do9n=$[$n +1 ]TenEcho Line $n: $var One  Done A  - $sh commandfor.sh -Line1: #!usr/bin/Bash theLine2: list01=' the -Line3: First - ... ... -Line -: Do +Line -: (( -Line -: n++ +Line -: )) A ... ... atLine to: $var -Line +: Done

1.5 changing field separators

1# environment variable ifs-internal Field delimiter2*default delimiter: spaces; tabs; line breaks3* Change: Single: ifs=$'\ n'-(line wrapping)4Multiple: ifs=$'\ n:; "'-(newline/colon/semicolon/double quotes)5*Save and Restore:6Ifs. Old=$IFS7ifs=$'\ n'8                 ...9ifs=$IFS. oldTen  One $cat commandfor.sh A#!usr/bin/Bash -n=0 -Ifs. Old=$IFS theifs=$'\ n' -  for var inch' Cat varfortest02.sh ' -  Do -n=$[$n +1 ] +Echo Line $n: $var -  Done +ifs=$IFS. old A  at $sh commandfor.sh -Commandfor.sh:line3: IFS. Old=: Command not found -Line1: #!usr/bin/Bash -Line2: list01='The first test example' -Line3: list02="The Second Test example" -Line4: list03= $list 02"The thrid Test Example" inLine5: list04=$list 01$list02$list03 -Line6: Echo $list toLine7: n=0 +Line8: for var inch$list -Line9: Do theLineTen: ((n++ )) *Line One: Echo Cycle $n: $var $Line A: Done

1.6 reading a file/directory with wildcard characters

1 # File/directory variables are enclosed in double quotation marks as far as possible.2 # File/directory lookup method and list method merge into the same for statement
* You can add any number of wildcards, the for statement first matches a file or directory to form a list, and then iterates through the list3 $cat filefor.sh4#!usr/bin/Bash5  forFileinch./*./TSTTST6  Do7 if [-E "$file"]8  Then9 echo the file is $fileTen Else One echo the Fiel $file do not exist! A fi -  Done -  the $sh filefor.sh - The file is./commandfor.sh - The file is./filefor.sh - The file is./fortest01.sh + The file is./varfortest02.sh - The fiel./tsttst do not exist!

[Linux] structured command-for