Display number of files at a time using the ls command

Question

I have a bash script that ask the person to first select an order at which the files in the current directory are displayed. Next I have them choose a file from a list that is created using a select loop. After they select a file it will ask them what type of command they would like to use. My issue is that I want to display only a certain number of files to the user at a time. Let's say I want to list 23 files at a time. How would I do that?

Sorry if it is sloppy

    ORDER=("name" "age" "size")
    select OPT4 in "${ORDER[@]}"
    do
            if [[ $OPT4 == "name" ]]
            then
                    ARRAY=( $( ls . ) )
    #               select OPT2 in "${ARRAY[@]}"
    #               do
    #                       echo $OPT2
    #               done
            fi
            if [[ $OPT4 == "age" ]]
            then
                    ARRAY=( $( ls -rt ) )
    #               select OPT2 in "${ARRAY[@]}"
    #               do
    #                       echo $OPT2
    #               done
            fi
            if [[ $OPT4 == "size" ]]
            then
                    ARRAY=( $( ls -S ) )
    #               select OPT2 in "${ARRAY[@]}"
    #               do
    #                       echo $OPT2
    #               done
            fi
    echo $OPT4
    #ARRAY=( $( ls -S ) )
    select OPT2 in "${ARRAY[@]}"
    do
            OPTIONS=("author" "type" "copy" "ren" "move" "del" "copy!" "ren!" "move!" "help")
            select OPT1 in "${OPTIONS[@]}"
            do
    if [[ $OPT1 == "copy!" || $OPT1 == "move!" || $OPT1 == "ren!" ]]
                    then
                            select OPT3 in "${ARRAY[@]}"
                            do
                            echo $OPT3
                            break
                            done
                    fi
                    if [[ $OPT1 == "copy" || $OPT == "move" || $OPT1 == "ren" ]]
                    then
                            echo -n "Enter a file destination: "
                            read OPT3
                    fi
                    case $OPT1 in
                            $AUTHOR)
                                    echo  "Last, First";;
                            $TYPE)
                                    exist
                                    file
                                    order66;;
                            $COPY)
                                    exist
                                    file
                                    order66;;
                            $RENAME)
                                    # mv &>/dev/null $2 $3;;
                                    exist
                                    file
                                    order66;;
                            $MOVE)
                                    # mv &>/dev/null $2 $3;;
                                    exist
                                    file
                                    order66;;
                            $DELETE)
                                    # rm -f &>/dev/null $2;;
                                    exist
                                    file
                                    order66;;
                            $FORCE_COPY)
                                exist
                                file
                                order67;;
                        $FORCE_MOVE)
                                exist
                                file
                                order67;;
                        $FORCE_RENAME)
                                exist
                                file
                                order67;;
                        $HELP)
                                echo -e $MESSAGE;;
                        *)
                                echo -e $MESSAGE;;
                esac
                exit
        done
done
done

Answer 1

Your best solution is to read the list of files into an array, and then implement a simple pager. You can then use a c-style for loop to keep track of the file indexes and act on the value of the loop index. The following shows implementation of the pager. What you will do to act on the index is just add to the read statement (eg: read -p "(#)Select File (f)orward (b)ack : " ans ) and include an else to handle the # ). I've posted the additional code for filename selection below the pager example.

The number of files shown per-page is controlled with the pg_size variable. Adjust as necessary. Likewise, you can control whether files are read recursively by adjusting the find statement filling the file array:

#!/bin/bash

declare -i pg_size=4

file_array=( $(find "$1" -maxdepth 1 -type f) )

for ((i=0; i<${#file_array[@]}; i++)); do

    echo "  ${i}.   ${file_array[$i]}"

    if [ "$i" -gt 0 -a $(((i+1)%pg_size)) -eq 0 ]; then
        read -p "(f)orward (b)ack : " ans
        if [ "$ans" = 'b' ]; then
            [ "$i" -gt "$((pg_size))" ] && ((i = i - (2*pg_size))) || ((i = i - pg_size))
        fi
    fi

done

output example:

$ ./lspager.sh tmp
  0.   tmp/File1950text.doc
  1.   tmp/vcs1dump
  2.   tmp/File2014text.xls
  3.   tmp/File307list.cvs
(f)orward (b)ack : b
  0.   tmp/File1950text.doc
  1.   tmp/vcs1dump
  2.   tmp/File2014text.xls
  3.   tmp/File307list.cvs
(f)orward (b)ack : f
  4.   tmp/vcsa1dump
  5.   tmp/File256name.txt
  6.   tmp/README.txt
  7.   tmp/dl
(f)orward (b)ack : b
  0.   tmp/File1950text.doc
  1.   tmp/vcs1dump
  2.   tmp/File2014text.xls
  3.   tmp/File307list.cvs
(f)orward (b)ack : f
  4.   tmp/vcsa1dump
  5.   tmp/File256name.txt
  6.   tmp/README.txt
  7.   tmp/dl
(f)orward (b)ack : f
  8.   tmp/File1949text.doc
  9.   tmp/vcsadump
  10.   tmp/vcsdump
  11.   tmp/helloworld.txt
(f)orward (b)ack : f
  12.   tmp/File1951text.dat

---

To implement the filename selection, simple add to the read and implement a test to validate a numeric answer within range and break out of the loop:

#!/bin/bash

declare -i pg_size=4

file_array=( $(find "$1" -maxdepth 1 -type f) )

for ((i=0; i<${#file_array[@]}; i++)); do

    echo "  ${i}.   ${file_array[$i]}"

    if [ "$i" -gt 0 -a $(((i+1)%pg_size)) -eq 0 ]; then
        read -p "(#)Select file (f)orward (b)ack : " ans
        if [ "$ans" = 'b' ]; then
            [ "$i" -gt "$((pg_size))" ] && ((i = i - (2*pg_size))) || ((i = i - pg_size))
        elif [[ "$ans" =~ [0-9] ]]; then  # note character class, [[, and =~ are bash only
            [ "$ans" -le "$i" ] && echo "You chose '$ans' - ${file_array[$ans]}" && break
        fi
    fi

done

output:

$ ./lspager.sh tmp
  0.   tmp/File1950text.doc
  1.   tmp/vcs1dump
  2.   tmp/File2014text.xls
  3.   tmp/File307list.cvs
(#)Select file (f)orward (b)ack : f
  4.   tmp/vcsa1dump
  5.   tmp/File256name.txt
  6.   tmp/README.txt
  7.   tmp/dl
(#)Select file (f)orward (b)ack : f
  8.   tmp/File1949text.doc
  9.   tmp/vcsadump
  10.   tmp/vcsdump
  11.   tmp/helloworld.txt
(#)Select file (f)orward (b)ack : b
  4.   tmp/vcsa1dump
  5.   tmp/File256name.txt
  6.   tmp/README.txt
  7.   tmp/dl
(#)Select file (f)orward (b)ack : 5
You chose '5' - tmp/File256name.txt