shell

Collection of helpful shell commands.

File system

# mount a samba share
mount -t cifs //192.168.0.42/share remote

User manipulation

# interactively add a user
adduser fred

# change user's password
passwd fred

# add user to group wheel
usermod -aG wheel fred

# remove user
deluser fred

# create a group
groupadd wheel

Archives

# create a gzipped tar file with intermediary file
tar cvf foo.tar foo1.txt foo2.txt
gzip -9 foo.tar

# create a gzipped tar file without intermediary file
tar cvf - foo1.txt foo2.txt | gzip -9 > foo.tar.gz

# GNU tar command
tar czf foo.tar.gz foo1.txt foo2.txt

# create a bzipped tar file (long version)
tar cf tarfile.tar.bz2 --use-compress-program=bzip2 foo1.txt foo2.txt

# create a bzipped tar file (newer versions of GNU tar)
tar cjf foo.tar.bz2 foo1.txt foo2.txt

Awk, Sed, Grep & scripting

# join each line with the next line
awk '{if (NR % 2) {prev=$0} else {print prev, $0}}'

# print third column in file
cat mystuff.txt | awk '{print $3}'

# remove first line and all whitespace from file `question1_file`:
cat question1_file | awk '{printf "%s", (NR==1 ? "" : $0)}' | tr -d '[:space:]'

# find emails in a file and write them to another file separated with commas:
cat text_with_emails.txt | grep -o '[^ ,]\+@[^ ,]\+\.[a-zA-Z]\+' | awk '{printf "%s"(NR==1 ? "" : ", "), $0}' > emails.csv

# remove unversioned files from svn tree (akin to bzr clean-tree)
svn status --no-ignore | grep '^\?' | sed -r 's/^\?\s+//' | xargs rm -rf

# kill moin fcgi processes (find them in ps listing, then kill)
ps aux | grep moin | awk '{print $2}' | sudo xargs kill

# sort by third column in file
sort -k3 mystuff.txt

# redirect both stderr and stdout to /dev/null
foobar > /dev/null 2>&1

# print only non-blank lines:
cat foobar.txt | grep -v '^\s*$'

Find files

Find php files in current directory ignoring SVN dirs:

$ find . -path '*.svn' -prune -o -path '*.php' -print

or

$ find . -name '.svn' -prune -o -name '*.php' -print

Find all files except SVN dirs:

$ find . -name '.svn' -prune -o -print

Apply chmod 644 to all files (not directories) in /usr/share/man:

$ find /usr/share/man -type f | xargs chmod 644

Search for __init__ only in python files:

$ find . -name "*.py" -exec grep '__init__' '{}' ; -print

Locate file named exactly foobar (not foobar)

$ locate -b '\foobar'

Remote interaction

Copy a directory to remote server via rsync through SSH

$ rsync -avz -e ssh localdir user@192.0.32.10:remotedir

Recursively download an FTP directory from a remote machine

# --continue, -c continue getting partially-downloaded file
# --no-clobber, -nc if file exists on disk, do not download it
# to avoid specifying password on the command line, put it in .wgetrc or .netrc
wget -r --no-clobber --continue --ftp-user=fredfoobar --ftp-password=mypass123 --level=100 ftp://ftp.example.com/remotedir

Do a DNS zone transfer (list all DNS records for a server)

$ dig @dns.example.com example.com axfr

# copy a public key to a remote machine
cat ~/.ssh/id_dsa.pub | ssh user@remote.machine.com 'cat >> .ssh/authorized_keys'

Make a post request to a webpage:

# curl -v -F "x=y" https://30daysofdirt.dialformen.com/enter

Code

Create a patch file

$ diff -Naur olddir newdir > new-patch

Apply patch

$ patch -p0 < new-patch

Compilation

Include debugging information:

$ gcc -g hello.c

Compile programs that use OpenGL

$ gcc -lGL -lGLU -lglut -o hello hello.c

Network configuration

Useful utilities