Doubt array of bash

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Doubt array of bash

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#1 by (3 votes)

1

I was trying to do the following: Make a script that adds to an array all the files in the / home directory whose termination is .doc
MY SOLUTION:

 vector=()  
 guardar=0  
 for i in 'find /home -name *.doc'; do       
      vector[$guardar]=$i        
     let guardar=guardar+1  
 done

Is it well done? Thanks for helping me

linux bash ubuntu

asked by Janzek 01.11.2018 в 22:44

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1 answer

Create 'struct' with string fields of a length or array char with a length How can I explicitly cast in an image? C #

score 3 · Answer 1

The biggest problem with this code is this part:

for i in 'find /home -name *.doc'

You probably think that the variable i takes the value of each line from the output of the find command, but this is not the case. Actually the following happens:

The find command is executed.

The output of the command suffers the effect known as word splitting .

The result of the previous step suffers the effect known as filename expansion .

The resulting elements are used by the for command to be assigned to the variable i in their corresponding iteration.

Put another way, the process will fail if any of the file names contain characters that cause filename expansion or word splitting . .

That is, if the output of find were this:

./archivo 1.doc
./archivo 2.doc
./archivo *.doc

The content of the array would be this (each line is an element of the array):

./archivo
1.doc
./archivo
2.doc
./archivo
archivo 1.doc
archivo 2.doc
archivo *.doc

On the other hand, it is not necessary to manually manage the array indexes. You can use the arreglo+=(elemento) syntax for Bash to do that work for you.

That said, I can think of at least two methods to deal with this situation.

Method 1: Filename expansion

This is the native method, but it is not as fast or as powerful as find :

for archivo in "${HOME}"/*.doc; do
  arreglo+=( "${archivo}" )
done

shopt -s dotglob globstar

for archivo in "${HOME}"/**/*.doc; do
  arreglo+=( "${archivo}" )
done

The first searches for files within the ${HOME} directory that match the *.doc pattern. The second does the same but recursively, including hidden directories.

Method 2: `mapfile` + process substitution

Useful if you prefer to use find but avoiding the effects of filename expansion , word splitting and the use of for :

mapfile -t arreglo < <(find "${HOME}" -name '*.doc')

With GNU find you could even use the -print0 option to avoid problems with line breaks in the file names:

mapfile -d '' -t arreglo < <(find "${HOME}" -name '*.doc' -print0)

Doubt array of bash

1 answer

Method 1: Filename expansion

Method 2: mapfile + process substitution

Method 2: `mapfile` + process substitution