===== File based utilities =====
==== Looking around ====
> Looking through files is done with the ''%%ls%%'' command under Linux, which is an abbreviation for ''%%list%%''.
By default (meaning without parameters) the ''%%ls%%'' command shows the content in the current directory. It does hide elements starting with a dot though. These hidden elements can be shown by adding the ''%%-a%%'' parameter, which stands for ''%%all%%''. If you want detailed information about the elements, add the ''%%-l%%'' parameter for ''%%long listing%%''. You can also specify a file/directory which you want to examine, by just appending the path to the command.
$ ls # shows files and directories
testdir test
$ ls -a # includes hidden ones
. .. testdir test
$ ls -l # detailed view
drwxr-xr-x 1 myuser p12345 0 Apr 13 2017 testdir
-rw-r--r-- 1 myuser p12345 4 Apr 13 11:55 test
$ ls /tmp/
allinea-USERNAME
ssh-6E553lWZCM
ssh-C6a754pJ1d
systemd-private-a4214393983d448fbdc689791806519c-ntpd.service-LrAgBP
tmp7CJZRA
yum_save_tx.2017-04-03.12-07.VCUowf.yumtx
$ ls -alh ~
drwxr-xr-x 5 myuser mygroup 45 Jan 30 2017 .allinea
-rw------- 1 myuser mygroup 21K May 3 17:14 .bash_history
-rw-r----- 1 myuser mygroup 231 Dec 2 2016 .bashrc
drwx------ 1 myuser mygroup 76 Aug 22 2017 Simulation
drwx------ 2 myuser mygroup 76 Dec 12 2016 .ssh
==== Moving around ====
> Moving through directories is done with the ''%%cd%%'' command, which stands for ''%%change directory%%''.
The ''%%cd%%'' command can be called without any arguments, in which case it just switches to the home directory. Otherwise it takes a absolute (starting with a dash) or relative path as an argument and switches to that directory. The argument ''%%-%%'' (just a single dash) will cause cd to switch to the previous directory. This can be used to alternate between two directories without typing their path’s every time.
$ cd /bin # go to an absolute directory
$ cd [~] # go home
$ cd - # go to previous directory
==== Copying & moving files around ====
> Copying and moving files and directories is done with the ''%%cp%%'' and ''%%mv%%'' commands, which stand for ''%%copy%%'' and ''%%move%%'' respectively.
Both commands take at least two parameters, which correspond to the ''%%%%'' and ''%%%%'' files or directories. For ''%%cp%%'' to work with directories as a source, it needs the ''%%-r%%'' (recursive) or ''%%-a%%'' (archive) flag.
> Beware of the pitfalls! you can overwrite data and therefor lose it, without getting any confirmation prompt! If in doubt use ''%%-i%%'' (interactive) flag.
$ mv old new # rename old to new
$ mv old dir/ # move old into dir
$ mv file1 file2 # overwrite file2 with file1
# (BEWARE)
$ cp -i input input.bak # input to input.bak
$ cp -i input backup/ # input into backup
$ cp -a dir1/ dir2 # exact copy of dir1
==== Creating and deleting ====
=== directories ===
> creating directories is done with the ''%%mkdir%%'' command, which stands for ''%%make directory%%''.
The ''%%mkdir%%'' command takes an optional ''%%-p%%'' (parents) parameter and a path. When optional parameter is given, it will create all the ancestors of the specified directory aswell. Otherwise the command fails if the directory either exists already or its parent doesn’t exist either.
> deleting directories is done with the ''%%rmdir%%'' command, which stands for ''%%remove directory%%''.
This command removes the specified directory, but only if it’s already empty. it can also take an optional ''%%-p%%'' parameter, in which case it removes the specified directory and all the ancestors you included.
==== Finding stuff ====
> To look at everything
- in your home directory
- and nested up to three levels deep inside it
- that ends in ''%%.txt%%''
- or starts with ''%%log_%%''
- and is an ordinary file
- concatenated as one stream:
find \
~ \
-maxdepth 3 \
-iname "*.txt" \
-or -iname "log_*" \
-type f \
-exec cat '{}' \; | less
find \
~ \
-maxdepth 3 \
-iname "*.txt" \
-or -iname "log_*" \
-type f \
-exec cat '{}' + | less
===== Content based utilities =====
==== Contents of files ====
> **viewing** is done by the **''%%less%%''** command:
> **concatenating** is done by the **''%%cat%%''** command:
$ less file.txt # exit with 'q'
$ less -R file.txt # keep colors
$ cat file1 file2 | less
$ cat file
$ cat -A printable
$ cat -n numbered
$ echo "VSC is great" > file
$ cat file
VSC is great
$ echo "VSC is awesome" >> file
$ cat file
VSC is great
VSC is awesome
$ cat file | grep awesome
VSC is awesome
$ grep awesome file
VSC is awesome
==== Space accounting ====
> viewing **used space** is done by the **''%%du%%''** (disk usage) command:
> viewing **free space** is done by the **''%%df%%''** (disk free) command:
$ du -h file1 file2 # human readable output
$ du -s dir # summarize
$ df -h # human readable output
$ df -t nfs # only list filesystems of a type
{{.:screenshot_df.png?0x440}}
==== Recap ====
$ mv space.log space.log.bak
$ df -h | grep "lv12345\|lv54321" > space.log
$ cat space.log
nfs05.ib.cluster:/e/lv12345 200G 185G 16G 93% /home/lv12345
nfs04.ib.cluster:/e/lv54321 1000G 979G 22G 98% /home/lv54321
> we do this often, let’s wrap it up!
==== Recap++ ====
$ mv space.log space.log.bak
$ df -h | grep "lv12345\|lv54321" > space.log
$ cat space.log
nfs05.ib.cluster:/e/lv12345 200G 185G 16G 93% /home/lv12345
nfs04.ib.cluster:/e/lv54321 1000G 979G 22G 98% /home/lv54321
> we do this often, let’s wrap it up!
$ echo '#!/bin/bash' > spacelog.sh
$ echo 'mv space.log space.log.bak' >> spacelog.sh
$ echo 'df -h | grep "lv12345\|lv54321" > space.log' >> spacelog.sh
$ echo 'cat space.log' >> spacelog.sh
$ chmod +x spacelog.sh
$ ./spacelog.sh
==== Sed and awk ====
> **sed** (stream editor) and **awk** are powerful tools when working with the command line
$ mycommand | sed "..."
$ mycommand | awk '{...}'
> Using sed and awk in action
^program ^ command ^description ^
|sed | ''%%s/old/new/%%'' |replace ''%%old%%'' with ''%%new%%'' |
|sed | ''%%/from/,/to/ s/old/new/%%'' |replace ''%%old%%'' with ''%%new%%'', between ''%%from%%'' and ''%%to%%'' |
|awk | ''%%'print $5 $3'%%'' |print columns 5 and 3 of every line |
Example script:
#!/bin/bash
mv space.log space.log.bak
df -h | grep "lv12345\|lv54321" > space.log
cat space.log
#!/bin/bash
mv space.log space.log.bak
df -h | grep "lv12345\|lv54321" > space.log
cat space.log | sed "s|/home/lv12345|ProjectA|" \
| awk '{print $6, "free:", $4}' \
| column -t