linuxstringbashtext-extraction

Extract output values from disk image file as strings in Linux

I have an .img file from which I would like to extract 2 values derived with fdisk, as strings in 2 variables.

fdisk -l /home/documents/image-of-sd-card.img
Disk /home/documents/image-of-sd-card.img: 14,84 GiB, 15931539456 bytes, 31116288 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0xc680d152

Device                                    Boot  Start      End  Sectors  Size Id Type
/home/documents/image-of-sd-card.img1        8192   655359   647168  316M  c W95 FAT32 (LBA)
/home/documents/image-of-sd-card.img2      655360 31115263 30459904 14,5G 83 Linux

The values I would need are the last unit from "Sector size" (512) and the End size of the second partition (31115263). How to achieve that? I would prefer a Bash based solution so that I could integrate this into an existing Shell script.

As an absolute beginner in Linux I just played around with some greb commands but to no avail.

Solution

  • Here a steps by step explanation to help you in your bash learning

    raw_content=$(fdisk -l /home/documents/image-of-sd-card.img)

sector_size=
second_partition_size=
while read i 
do 

    if [[ "$i" == "Sector size"* ]]; then
        echo ">>>>$i" 
        echo "$i" | cut -d ' ' -f 7
        sector_size=$(echo "$i" | cut -d ' ' -f 7)
    elif [[ "$i" == "/home/documents/image-of-sd-card.img2"* ]]; then
        echo ">>>>$i" 
        echo "$i" | awk -F' ' '{ print $3 }'
        second_partition_size=$(echo "$i" | awk -F' ' '{ print $3 }')        
    fi

done <<< "$raw_content"

echo -e "\nResults:"

echo "sector_size: $sector_size"
echo "second_partition_size: $second_partition_size"

    Output:

    Explanation

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