• find files/directories/named pipes/etc.
• See examples here.
  • -exec option allows running a command on the find results.
    • Not everything is possible with find's -exec option.
      • A shell for loop may be more appropriate instead.

• find is sometimes recommended over ls in certain situations.

• Quickly locate a file on a local filesystem.
  • Use locate
  • If set up on the system, can find files rapidly using locate filename.

• execute commands on a collection of arguments
• See examples here.
• Also see examples in the xargs man page.
• Often used at the back end of a find command because it's more capable than find's -exec option.

# Find all hidden files (files that begin with period ".*"),
# starting in the current dir, and then use xargs to run "ls -l"
# on all the find results.
$ find . -type f -name '.*' | xargs ls -l

# Same output as 
# $ find . -type f -name '.*' -exec ls -l {} \;



# List all users logged in and run finger on each userid
$ w -h | awk '{ print $1 }' | sort | uniq | xargs finger
#
# w -h               - list logged in users and associated info, excluding header (-h)
# awk '{ print $1 }' - print only userid from w output
# sort | uniq        - reduce duplicates
# xargs finger       - run finger on list of users from uniq

• Tape Archive (See article.)
• Archive file/dirs, preserving file/dir attributes.
  • Usually operate on directories, not files.
• Common options:

        c - create archive
        t - view existing archive
        v - operate verbosely
        x - extract archive
        f - create the specified tar file ( or use "-" to send tar'ed
            files to stdout ) 

• Examples:

# Create tar archive (cs370.tar) of your ~/cs370 directory in /tmp:
# Dashes ("-") are optional for tar options.
$ tar cvf /tmp/cs370-${USER}.tar ~/cs370  # "tar -cvf ..." does the same thing

# Change to /tmp
$ cd /tmp

# "tar tvf cs370-${USER}.tar" shows the contents of cs370.tar.
# "tar xvf cs370-${USER}.tar" extracts the contents of cs370.tar to
# the CURRENT directory. (BE CAREFUL.)

• Since .tar archive are not compressed, tar is often used in combination with a file compressor such as gzip, bzip2 or xz. See examples below.

• Compression of single files
  • gzip is faster; bzip2 compresses more; xz compresses better than bzip2 and is faster.
  • See article on gzip and bzip2.
  • See information on xz format.

• Compress individual files:

$ cd /tmp

# Copy nano config files to /tmp
$ cp /usr/share/nano/*.nanorc  /tmp

$ gzip *.nanorc    # will result in all .nanorc files in current dir
                   # being compressed and given the .nanorc.gz extension


$ gunzip *.gz      # will uncompress the .nanorc.gz files and
                   # leave files w/ .nanorc extensions


$ bzip2 *.nanorc
$ bunzip2 *.bz2    # same as above, but with bzip2


$ xz *.nanorc
$ unxz *.xz        # same as above, but with xz

• Use “-c” option to gzip, bzip2 and xz send compressed data to stdout

# Copy large wordlist to /tmp
$ cp /usr/share/dict/words  /tmp

# Compress wordlist to a separate compressed files:
$ gzip -c words > words.gz
$ bzip2 -c words > words.bz2
$ xz -c words > words.xz
# Compare size of compressed file formats.
# Also try zip:
$ zip words.zip words

• View compressed text files
  • On most Linux systems, program documentation under /usr/share/doc is usually compressed to save space.

# View nano documentation
$ cd /usr/share/doc/nano
$ ls

# View a compressed file (NEWS.gz)
$ gunzip -c NEWS.gz | less

or, more simply,

$ zless NEWS.gz

# Cat a compressed file (NEWS.gz)
$ zcat NEWS.gz:

• gzip/bzip2/xz are often used in combination with tar.

# Tar your ~/cs370 dir to tar's stdout (-) and xz it,
# redirecting the result to cs370.tar.xz:
$ tar cvf -  ~/cs370 | xz -c > /tmp/cs370-${USER}.tar.xz

# Change to /tmp
$ cd /tmp

# Do the reverse to view contents of cs370-${USER}.tar.xz:
$ unxz -c cs370-${USER}.tar.xz | tar tvf -

• GNU tar (the version most widely used) has command line options that make it much easier to compress tar archives with gzip, bzip2 and xz:

$ tar cvJf /tmp/cs370-${USER}.tar.xz ~/cs370 
# GNU tar's "J" option forces use of xz to compress the tar archive
#        if "z"        uses          gzip
#        if "j"        uses          bzip2

# to view tar.xz    
$ tar tvJf cs370-${USER}.tar.xz

# to extract tar.xz 
$ cd /tmp; tar xvJf cs370-${USER}.tar.xz

• Venerable remote login and file transfer programs
  • contain known security vulnerabilities
• Should avoid using, especially on older, legacy systems.
• Telnet sometimes useful for querying network ports for services

# Check if vnc service running on plato (port 5900)
# Any response means the service is running
telnet plato 5900

• Secure Shell and Secure Copy
  • verify ssh setup from week 1
• More secure and versatile remote login and file transfer programs
  • See article on ssh security mechanisms.
• ssh is used as both a remote login program and remote command execution method:

• Warning about running programs through ~/.bashrc and their possible effects on ssh/scp.

#
# Remote login:
#

# Login remotely to rockhopper.
# Authenticate using either a password or encrypted
# key exchange:
$ ssh <your_userid>@rockhopper

# See verbose output of a ssh login process
$ ssh -v <your_userid>@rockhopper


#
# Remote command execution:
#

# Run the 'uptime' command on plato:
$ ssh plato 'uptime'

# See logins on rockhopper
$ ssh rockhopper 'finger'

# See jchung logins on rockhopper
$ ssh rockhopper 'finger | grep -i chung'

# Same thing, but stdout from rockhopper piped to local grep
$ ssh rockhopper 'finger' | grep -i chung


# Tar your ~/cs370 dir locally, pipe to gzip on rockhopper to
# create rockhopper:/tmp/$USER-cs370.tar.gz:
$ tar cvf -  ~/cs370 | ssh rockhopper "gzip -c > /tmp/$USER-cs370.tar.gz"

• Remote file transfers with scp (uses same authentication mechanism as ssh):

# Create and transfer /tmp/cs370.tar.xz to your home dir on the plato server:
$ tar  cJf  /tmp/cs370.tar.xz  ~/cs370
$ scp  /tmp/cs370.tar.xz  plato:~


# Transfer ~/cs370.tar.xz from plato to local /tmp:
$ scp  plato:~/cs370.tar.xz  /tmp

• Remote Sync (See article)
• More efficient file transfer program that is useful for keeping remote directories synchronized with local ones
  • Rsync algorithm transfers differences between local and remote copies of files, rather than entire files.
• Uses ssh authentication by default

# Transfer entire ~/cs370 dir to a remote machine:/tmp
# rsync command options (similar to cp options)
#   -a archive (recursively copy dirs and preserve all file/dir attributes)
#   -u update  (only transfer files that are newer than destination)
#   -v verbose
# 
# In this rsync command, the source is ~/cs370 and the destination is localhost:/tmp.
$ rsync -auv  ~/cs370  localhost:/tmp

# Run it again.
# Since -u (update) is being used, nothing gets transferred because the source
# and destination are both up-to-date.
$ rsync -auv  ~/cs370  localhost:/tmp

# Update timestamp of ~/cs370/examples dir with 'touch',
# and run rsync again.
$ touch ~/cs370/examples
$ rsync -auv  ~/cs370  localhost:/tmp

• Web Get (See article)
• non-interactive URL download program
• Default mode: download and save html file at specified URL

$ wget "http://wikiless.tiekoetter.com/wiki/regular_expressions"
	  
# Saves article to file "regular_expressions".

• -O file_name option saves to specified file_name.
  • -O - sends html to stdout.

• The cURL utility has similar functionality and is simpler.

• To work well with other programs (see the UNIX philosophy), utilities like tar and wget allow the use of the “-” (STDOUT) convention.
  • Output that would normally be sent to a file is sent instead to STDOUT with “-”.
    • tar cvf - ~/cs370 # (sends tar archive data to STDOUT instead of to a .tar file)
    • wget -O - http://monmouth.edu # (sends retrieved URL to STDOUT instead of to a file)
  • A third utility we've looked at, enscript, also uses the “-” convention.

• Run the following commands first:

mkdir -p ~/cs370/examples/revcontrol
cd ~/cs370/examples/revcontrol
wget -q http://bit.ly/2zZgGiV -O diffpatch.tar.xz # download diffpatch.tar.xz
tar xvJf diffpatch.tar.xz                         # extract the diffpatch directory
ls
cd diffpatch

• diff
  • compares 2 files and displays a list of editing changes that would convert the first file into the second file.
    • The 3 kinds of editing changes are a-add lines, c-change lines, and d-delete lines.

        SYNOPSIS
               diff [options] from-file to-file

• Examples:

# diff input file #1
# saved as seuss1
$ cat seuss1
If a packet hits a pocket on a socket on a port,
and the bus is interrupted at a very last resort,  
and the access of the memory makes your floppy disk abort,
then the socket packet pocket has an error to report.




# diff input file #2
# saved as seuss2
$ cat seuss2
If a pocket hits a rocket on a socket on a port,
and the bus is interrupted at a very last resort,  
and the access of the memory makes your floppy abort,
then the socket packet pocket has an error to report.


       


# Use diff to show differences between seuss1 and seuss2:
$ diff seuss1 seuss2
1c1
< If a packet hits a pocket on a socket on a port,
---
> If a pocket hits a rocket on a socket on a port,
3c3
< and the access of the memory makes your floppy disk abort,
---
> and the access of the memory makes your floppy abort,



# diff input file #3
# saved as seuss3
$ cat seuss3
If a pocket hits a rocket on a socket on a port,
and the bus is interrupted at a very last resort,  
and the access of the memory makes your floppy abort,
then the socket packet pocket has an error to report.
       
If your cursor finds a menu item followed by a dash,
and the double-clicking icon puts your window in the trash,
and your data is corrupted cause the index doesn't hash,
then your situation's hopeless and your system's gonna crash!




       
# Use diff to show differences between seuss2 and seuss3:
$ diff seuss2 seuss3
4a5,9
> 
> If your cursor finds a menu item followed by a dash,
> and the double-clicking icon puts your window in the trash,
> and your data is corrupted cause the index doesn't hash,
> then your situation's hopeless and your system's gonna crash!





# diff input file #4
# saved as seuss4
$ cat seuss4
If a packet hits a pocket on a socket on a port,
and the access of the memory makes your floppy disk abort,
and the bus is interrupted at a very last resort,  
then the socket packet pocket has an error to report.






# Use diff to show differences between seuss3 and seuss4:
$ diff seuss3 seuss4
1c1,2
< If a pocket hits a rocket on a socket on a port,
---
> If a packet hits a pocket on a socket on a port,
> and the access of the memory makes your floppy disk abort,
3d3
< and the access of the memory makes your floppy abort,
5,9d4
< 
< If your cursor finds a menu item followed by a dash,
< and the double-clicking icon puts your window in the trash,
< and your data is corrupted cause the index doesn't hash,
< then your situation's hopeless and your system's gonna crash!

        SYNOPSIS
               patch [options] [originalfile [patchfile]]

• Example:

# Using diff and patch to merge changes
$ diff seuss3 seuss4 > diff34        # Generate diff file


$ cp seuss3 seuss3.orig              # Backup original seuss3



$ patch --verbose seuss3 diff34      # Apply diff34 to seuss3
Hmm...  Looks like a normal diff to me...
Patching file seuss3 using Plan A...
Hunk #1 succeeded at 1.
Hunk #2 succeeded at 4.
Hunk #3 succeeded at 5.
done






$ cat seuss3         # seuss3 is now the same as seuss4
If a packet hits a pocket on a socket on a port,
and the access of the memory makes your floppy disk abort,
and the bus is interrupted at a very last resort,
then the socket packet pocket has an error to report.

• version control systems (VCS)
• Help to keep track of versions of files.
  • Store the differences between versions of files, rather than entire versions of files.
    • Saves space.
    • UNIX diff command or equivalent functionality plays a part in defining differences between versions of files.
• Plays an important role in software development, particularly team development
  • Single user version control systems: RCS
  • Multi-user version control systems: CVS, Subversion, Git, Mercurial
    • Centralized: CVS, Subversion
    • Decentralized: Git, Mercurial

In ~/.bashrc, define a shell function called searchfiles which uses find to list all files that contain the string (or regular expression) that you pass in as the first function parameter, $1. Note that we don't want to search file names but file contents for a string, and then list the files that match.

Answer:

# function searchfiles which uses find to list all files that 
# contain the string (or regular expression)
# that you pass in as the first function parameter, $1.
function searchfiles
{
   find . -type f |                 # list all files recursively starting in . (current dir)
   xargs grep -li "$1" 2> /dev/null # using xargs, make grep list files (-l) in which a match is found
	
   # Can also use command substitution, if not too many find results:
   # grep -li "$1" $(find . -type f) 2> /dev/null
   # 
   # If using GNU grep (most UNIX systems), can use just grep recursively (-r):
   # grep -rli "$1" 2> /dev/null
}

In ~/.bashrc, define a shell function called findcd that changes to a directory based on a find result. If what you're searching for matches a filename, then change to the directory where that file resides. If what you're searching for matches a directory name, then change to that directory.

Example usage:

# Change to a dir named randomwall or to a dir that contains a file called randomwall
findcd randomwall 

# Change to a dir named examples  
findcd examples

# Change to a dir that contains a file called roster
findcd roster

• Note: This should be a function and not a shell script because shell scripts run in their own sub-shells.

Answer:

# function findcd - changes to a directory based on the first hit from a find
function findcd
{
   # "head -n1" chooses first find result;
   # use head instead of tail here, else may have 
   # to wait for find to print many search results;
   # if find finds nothing, $findresult is ""
   findresult=$(find . -iname "*$1*" | head -n1)

   # If $findresult is a file, can't cd to it,
   # so have to trim $findresult to a directory
   if [ -f "$findresult" ]; then
      filename=$(basename "$findresult") # see man basename
      # delete $filename from end (\$) of $findresult
      findresult=$(echo "$findresult" | sed "s/$filename\$//")
   fi

   cd "$findresult" # If $findresult is "", nothing happens.
}

Within your home directory, find the maximum depth of a directory. Your results should include the directory's name.

Note: You'll need to use the find command's -printf option. See man find.

Answer:

# Starting in current directory (.), find directories (-type d), 
# print the depth of each directory found (-printf "%d "),
# print the path of each directory found (-print),
# do a descending, numeric sort (-rn), show only the first result (head -n1)
find . -type d -printf '%d ' -print | sort -rn | head -n1

or

find . -type d -printf '%d ' -exec ls -ld {} ';' | sort -rn | head -n1

• Login to gitlab at cssegit.monmouth.edu.

• Set up SSH login to gitlab. You should have created a SSH private/public key pair in Week 1).
  • The ssh_setup.sh script can be used to check your SSH keys setup.
  • NOTE: Add a SSH key to your gitlab profile before creating any new projects on gitlab.

• Back up your course directory (~/cs370 or ~/se370) using cp or rsync:

# Using cp
cp  -av  ~/cs370  ~/cs370-$(date +%m%d%y)

# or using rsync
rsync -av  ~/cs370  ~/cs370-$(date +%m%d%y)

• Create a new repository (project) on gitlab.
  • DO NOT include a README when creating the project.
  • Make it a private project.
  • Follow the instructions on gitlab under “Push an existing folder” to git-initialize your UNIX account course directory and push the contents to gitlab.

• Add user jchung as a member of your gitlab project (member type: Reporter).

• If git commandline retrieval and push operations require a userid and password to be entered even though you added your SSH public key to your gitlab profile, then see this possible solution (reddit).