Linux - File

Linux file management

• Linux - How to edit a file?
• Linux - How to transfer files between systems (such as Windows and Linux)
• Linux - File/Folder Permissions - Access Control List (ACL) - Posix Model

Sh - Hidden files

See Linux - Stat (File status)

Using Parameters Expansion Removal

fileFullName=$(basename "$filePath")
# or
fileFullName="${filePath##*/}"
extension="${fileFullName##*.}"
filename="${fileFullName%.*}"

• From a path string where the file does not exist

VAR=/filedoesnt/exist
echo ${VAR%/*}

/filedoesnt

• dirname returns the first parent of an existing path file.

dirname "dir/file"

dir

Linux - File/Folder Permissions - Access Control List (ACL) - Posix Model

if [ ! -f $PATH ]; then
    echo "File $PATH not found!"
fi

ABSOLUTE_PATH=$(realpath "${FILE_NAME}")

with Linux - ls (List directory content)

ls -lh myFile | awk '{ print $5 }'

where:

• -lh shows a human readable size
• an awk will extract the 5de column of the ls output

Example:

# the program that run
program=unzip
# the log of the progam
logfile='restoreAll.log'
# Don't touch below, the program
count=0
while kill -0 $(pgrep ${program}) 2> /dev/null; do
    count=$(( $count + 1 ))
	size=$(ls -lh ${logfile} | awk '{ print $5 }')
    echo "${count} - Process is running and the log is ${size}"
    sleep 10
done
echo "${count} - Process has exited"

cmp --silent $old $new || echo "files are different"
cmp -b $old $new 

See also : diff

diff file1 file2 | cat -t

where:

• ^M for CR,
• ^I for tab

See also: comparison

• Using grep

This command below gives you all files in the current directory which begin by elfutils

dir | grep -i elfutils

elfutils-0.137-3.el5.i386.rpm
elfutils-devel-0.137-3.el5.i386.rpm
elfutils-devel-static-0.137-3.el5.i386.rpm
elfutils-libelf-0.137-3.el5.i386.rpm
elfutils-libelf-devel-0.137-3.el5.i386.rpm
elfutils-libelf-devel-static-0.137-3.el5.i386.rpm
elfutils-libs-0.137-3.el5.i386.rpm

• find can do it recursviely

Permission: In UNIX and Linux, the ability to remove a file is determined by the access bits of parent directory

chmod 777 .
chown hi-adm:hi-adm .

With the command rm

Example:

• Basic

rm filename.extension

• Prompts for confirmation before removing a file

rm -i filename.extension

• Force removal of the file regardless of it bieng write-protected or open

rm -f filename.extension

• Remove files recursively in 'directory'

rm -r directory

More … perform the man commando

man rm

cp - Copy one or more files to another location.

Example::

• Copy of a directory with resistivity:

cp -r dirtocopy newdir

• Copy two files

cp myFile1.txt myFile2.txt myDirDestination

• Copy all files of directory

cp * myDirDestination
# or
cp /myDirSource/* /myDirDestination

• Copy all txt files (with a pattern)

cp *.txt myDirDestination

• mv - Moves or renames file

Example:

mv file.log file.$(date "+%Y.%m.%d-%H.%M.%S").log

cat file1 file2 > finalFile

# example with cert
cat first_cert.pem second_cert.pem > combined_cert.pem

• Linux Utility - Scp (secure copy, remote file copy) command

• Shell Data Processing - Cat command (short for concatenate),
• Shell Data Processing - Head (Displays first 10 lines of file),
• tail - Displays last 10 lines of file,
• Shell Data Processing - Tac (for reverse output) (for reverse output)
• less and more let you scroll the text files

• locate - List files that match a pattern.

Locate all file with a regular expression. In this example all file which begin with sp and end up with the extension msb.

locate -r "sp.*\.msb"

• find - search for files in a directory hierarchy.

find /my/directory -name myFile.extension

touch -d '2011-12-31 10:22' foo
find . -newer foo

See all other files in the time section of the find command

Shell Data Processing - Global Regular Expression Print (GREP command) (line filtering, word search)

• For the current directory .

grep -rn "string*" .

File Architecture

file fileName

Example:

file java

/bin/java: ELF 64-bit LSB executable, AMD x86-64, version 1 (SYSV), for GNU/Linux 2.6.9, dynamically linked (uses shared libs), for GNU/Linux 2.6.9, not stripped

OLDIFS=$IFS; IFS=$'\n'; 
filelines=`cat $filename`
for line in $filelines ; do
    echo $line
done
IFS=$OLDIFS

See setcap - set file capabilities.

A file may also be an executable one and they may got capabilities such as be able to take the port 80

• Bash - How to parse a CSV (Or properties files)

• ls - List contents of a directory
• which - Displays path to command
• whereis - locate the binary, source, and manual page files for a command

• Shell Data Processing - (WC|Word Count) command (Line count)
• Shell Data Processing - Uniq ("unique") - duplicate line removing: returns a file where the line are unique
• Shell Data Processing - Sort (the content of a file line by line)
• Shell Data Processing - Sed (Stream editor)
• Shell Data Processing - Global Regular Expression Print (GREP command) (line filtering, word search)
• Shell Data Processing - Awk (grep and sed) - Output filtering