Operating systems 1 -- 2008-2009 -- info.uvt.ro/Laboratory 2
Quick links: front; laboratories agenda, 1, 2, 3, 4, 5, 6, projects, evaluation, tools, references.
- examples:
- absolute paths:
/home/ciprian/test.sh /tmp
- relative paths:
./test.sh a/b/c ../a/b/c test.sh
- ~ expansion:
~/abc
POP PLAYER commands
edit- syntax:
- a list of blank separated words (strings);
- the first word specifies the command to be invoked;
- the remaining words are passed as arguments;
- the end is marked by a control character:
- end of line;
- &, &&, ||, ;;
<command> [<argument>] ...
- examples:
- prints Hello world:
echo Hello world! echo 'Hello world!'
- displays the manual page for bash:
- use q to exit;
- displays the manual page for bash:
man bash
- displays the current user:
whoami
List of commands
edit- syntax:
- a list of simple commands;
- separated by: ;, &&, ||;
- optionally terminated by ; or &;
- attention to the spacing;
<command> [argument] ... { <; | && | ||> <command> [argument] ... } ...
- example:
- displays hello world on two distinct lines:
echo hello ; echo world
- displays the date at two seconds apart:
date ; sleep 2 ; date
Comments
edit- in almost all situations characters following a # and up to the end of the line are treated as a comment:
echo a # b c
Basic bash script
edit- editing:
nano ./test.sh
- example script:
#!/bin/bash echo hello world exit 0
- making it executable:
chmod +x ./test.sh
- executing it:
./test.sh
Generic commands
editFile system commands
edit- references:
Current directory
edit- syntax:
pwd cd cd <directory>
- examples:
pwd cd /tmp pwd cd pwd
Viewing
editcat
edit- syntax:
cat [flag] ... [files] ...
- example:
cat ./test.sh cat -n ./test.sh
- important flags:
- -b or --number-nonblank;
- -n or --number;
- -s or --squeeze-nonblank;
- references:
stat and file
edit- syntax:
stat <file> ... file <file> ...
- examples:
- detailed information about a file or directory:
stat /etc stat /etc/group
- type information about a file or directory:
file /etc/group file /bin/bash
less and more
edit- syntax:
less [file] more [file]
- examples:
- displays the content of the /etc/services file:
- use q to exit;
- displays the content of the /etc/services file:
less /etc/services more /etc/services cat /etc/services | less
Directory creation
edit- syntax:
mkdir [flag] ... <directory>
- example:
- shows that the directory dir1 does not exist (in the current working directory);
- creates the directory dir1;
stat ./dir1 mkdir ./dir1 stat ./dir1
- creates a directory and its parents:
mkdir ./dir2/dir3 mkdir -p ./dir2/dir3
- important flags:
- -p or --parrents;
- references:
Directory deletion
edit- syntax:
rmdir [flag] ... <directory>
- example:
- deletes the empty folder dir1:
stat ./dir1 rmdir ./dir1 stat ./dir1
- deletes the empty folder and its (empty parents):
rmdir ./dir2/dir3 rmdir -p ./dir2/dir3
- important flags:
- -p or --parrents;
- references:
File creation
edit- syntax:
touch <file>
- example:
- shows that the file file1 does not exist and creates it:
stat ./file1 touch ./file1
- shows that if the file already exists it's left as it is (only the timestamp is modified):
stat ./file1 touch ./file1 stat ./file1
File deletion
edit- syntax:
rm [flag] ... <file> ...
- example:
- deletes the file file1
stat ./file1 rm ./file1 stat ./file1
- it demonstrates that we can not delete a directory that contains files or other folders:
mkdir dir4 touch dir4/file4 rm dir4
- we have to delete its children first:
rm dir4/file4 dir4
- or we can use the -R (recursive) flag to delete the directory and its children in one step:
mkdir dir5 touch dir5/file5 rm -R dir5
- important flags:
- -i or --interactive;
- -R or --recursive;
- references:
Copying
edit- syntax:
cp [flag] ... <sourc> <target>
- example:
- copying only one file:
cp /etc/group . stat ./group
- copying one file under a new name:
cp /etc/passwd ./passwd-copyied stat ./passwd-copyied
- creating a directory hierarchy:
mkdir ./dir6 cp ./group ./dir6 stat ./dir6/group
- trying to copy a directory (does not work unless we give it the -R flag):
cp ./dir6 ./dir7
- using the -R flag:
cp -R ./dir6 ./dir7 stat ./dir7/group
- showing that cp overwrites the destination file (if it exists):
cat ./group cp /etc/passwd ./group cat ./group
- important flags:
- -i or --interactive;
- -R or --recursive;
- references:
- cp.1;
Moving
edit- syntax:
mv [flag] ... <sourc> <target>
- examples:
- renaming a directory under one that already exists should not work:
stat ./dir6 stat ./dir7 mv ./dir6 ./dir7
- but we can rename it under a name that does not exist:
- we demonstrate that mv moves the entire hierarchy (without -R);
- but we can rename it under a name that does not exist:
mv ./dir6 ./dir8 stat ./dir8/group
- mv overwrites the destination file (just like cp):
cat ./passwd-copyied cp /etc/group ./group cat ./group mv ./passwd-copyed ./group cat ./group
- important flags:
- -i or --interactive;
- -R or --recursive;
- references:
- mv.1;
Querying
editls
edit- syntax
ls [flag] ... <directory>
- examples:
ls /tmp ls ~ ls -a ~ ls -l ~ ls -a -l ~ ls -al ~ ls /etc ls -1 /etc
- important flags:
- -a or -A;
- -l (with -h and / or -n);
- -1;
- references:
- ls.1;
find
edit- syntax:
find <directory> [test] ... [action] ...
- examples:
find /etc find /etc -type d find /etc -type f find /etc -name 'g*'
- important (flags) tests:
- -type;
- -name and -iname;
- important actions:
- -print;
- -ls;
- -exec;
- references: