Linux - File

About

Linux file management

Basic

Type

hidden

A full stop '.' before the name of the file makes it a hidden file. Example '.bash'

Sh - Hidden files

Metadata

Management

Get

Filename and extension

Using Parameters Expansion Removal

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

parent directory

  • 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

File Permission

File exist

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

Absolute path

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

Size

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

Monitoring the size of a (log) file

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"

Comparison

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

See also : diff

Diff

diff file1 file2 | cat -t

where:

  • ^M for CR,
  • ^I for tab

See also: comparison

Filter a list of files ?

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

Remove a file?

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

Copy 1 or multiple file

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

Move / Rename

  • mv - Moves or renames file

Example:

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

Concatenate

cat file1 file2 > finalFile

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

Transfer

See the content

Search a file by name

  • 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 /my/directory -name myFile.extension
#
find /my/directory -name globPattern

Search files based on time

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

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

Search the content of files

File Architecture (32 or 64 bit)

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

Iterate

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

Security / Capabilty

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

Processing

List of command

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

Content


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