Advanced Bash Scripting --- Russian

�� Bash:

�� Bash

Mendel Cooper

Brindlesoft

thegrendel@theriver.com

�� , �� (... � �� UNIX). �� , �� , � �� . �� , �� .

Dedication

For Anita, the source of all the magic

�� 1. ��

Shell (�� ) �� . �� , �� , �� . �� , �� , �� , ��, � �� . �� UNIX. � �� , �� . �� .

�� 1. �� ?

�� , �� . ��, �� Linux ��, �� /etc/rc.d �� . �� .

�� , �� , � �� [1]. �� , �� "��". �� , � �� .

�� "�� " �� . �� (�� ) �� - �� . � �� , � �� , ��++, Java, �� Perl.

�� UNIX, �� , �� . �� , �� , �� , �� Perl. �� , �� - �� , �� .

��

* ��, �� , �� (��, �� , ��.)
* ��, �� , � �� (��), �� , �� (�� ++ �� FORTRAN)
* �� -�� (�� ), ��
* �� (�� , �� , ��.)
* ��
* �� , �� , ��, � ��
* ��
* �� (Bash �� , � �� )
* ��
* �� , ��
* ��
* ��
* �� /��
* ��
* �� , �� (�� )

� �� , �� , �� , �� Perl, Tcl, Python, �� , ��++, �� Java. �� .

�� Bash. �� , "Bourne-Again Shell", �� , �� - Bourne Shell. Bash �� UNIX. �� , � �� Korn Shell, �� Bash[2], � �� C Shell � �� . (�� C Shell �� , �� (Tom Christiansen) � �� 1993 ��.

�� . �� , �� , � �� . �� , �� , � �� . �� -�� , �� (��_��_��.sh), �� (chmod u+rx ��_��_��.sh)[3] � �� . �� , �� . �� , �� .

�� , �� , �� .

��

[1]
�� , �� .

[2]
� Bash �� ksh88 � �� -�� ksh93.

[3]
�� , �� Bourne, �� .sh. �� , ��, � �� , �� /etc/rc.d.

�� 2. �� .

�� , �� . �� .

�� 2-1. ��: �� , �� (��) �� /var/log
# ��
# ��, ��

cd /var/log
cat /dev/null > messages
cat /dev/null > wtmp
echo "�� ."

�� , �� , �� xterm. �� . �� , ��, �� -�� .

�� 2-2. ��: ��
#!/bin/bash
# ��, �� 2
# �� .

LOG_DIR=/var/log
ROOT_UID=0     # �� $UID �� 0 �� (root).
LINES=50       # �� .
E_XCD=66       # �� ?
E_NOTROOT=67   # �� , �� -��.

if [ "$UID" -ne "$ROOT_UID" ]
then
echo "�� ."
exit $E_NOTROOT
fi

if [ -n "$1" ]
# ��, ��-�� (�.�. �� ).
then
lines=$1
else
lines=$LINES # �� , �� .
fi

#��
#��
#�� (�� ), ��
#�� , ��
#�� .
#
#    E_WRONGARGS=65 # �� (�� )
#
#    case "$1" in
#    ""      ) lines=50;;
#    *[!0-9]*) echo "��: `basename $0` ��-��-��"; exit $E_WRONGARGS;;
#    *       ) lines=$1;;
#    esac
#
#* �� , �� "�� ".

cd $LOG_DIR

if [ `pwd` != "$LOG_DIR" ] # �� if [ "$PWD" != "LOG_DIR" ]
# �� /var/log?
then
echo "�� $LOG_DIR."
exit $E_XCD
fi # �� "��" �� .

# �� :
# ---
# cd /var/log || {
# echo "�� ." >&2
# exit $E_XCD;
# }

tail -$lines messages > mesg.temp # �� .
mv mesg.temp messages # �� .

# cat /dev/null > messages
#* �� , �� , �� , �� .

cat /dev/null > wtmp # > wtemp �� -�� .
echo "�� ."

exit 0
# �� , �� , ��
# �� .

�� , �� . �� .

�� (#!) � �� . ��-�� #! �� "�� " �� [1] �� , � � �� (�� , �� "�� " (man magic)). �� . �� , �� , �� , �� . �� , �� (� �� ) �� [2].

#!/bin/sh
#!/bin/bash
#!/usr/bin/perl
#!/usr/bin/tcl
#!/bin/sed -f
#!/usr/awk -f

�� , �� , �� , �� /bin/sh, �� (bash �� Linux) �� -�� [3]. �� #!/bin/sh, �.�. �� Bourne Shell, �� UNIX, �� Linux, �� Bash (�� POSIX[4] �� sh). �� , �� "��" �� , �� , �� "�� " ("Command not found") �� .

#! �� . �� 2 �� , �� #! �� , lines=50, �� . ��, �� #!/bin/sh �� , �� , �� Linux �� /bin/bash.

��

�� . �� . �� . � ��, �� , �� .

if [ $# -ne ��_��_�� ]
then
echo "��: `basename $0` �� "
exit $WRONG_ARGS
fi

��

[1]

�� UNIX �� "�� " �� , �� !, #! /bin/sh.

[2]

� �� #! �� (sh �� bash) � �� . �� #, �� . �� , �� .

[3]

�� .

#!/bin/rm
# �� .

# �� , �� ... �� , �� .

WHATEVER=65

echo "�� ?"

exit $WHATEVER # �� . �� .

�� #!/bin/more �� (README) � �� . �� .

[4]

Portable Operating System Interface (�� ), �� UNIX�� .

2.1. �� .

�� , �� sh ��_��_��_�� [1] �� bash ��_��_��_��. (�� sh <��_��_��_��, �� (stdin).) �� chmod.

�� :

chmod 555 ��_��_��_�� (�� ) [2]

chmod +rx ��_��_��_�� (�� )

chmod u+rx ��_��_��_�� (�� )

�� , �� ./��_��_��_��[3]. �� "��" �� .

� �� /usr/local/bin (��, �� ) �� . �� _��_��_��[��] �� .

��

[1]
��: �� Bash �� sh ��_��_��_�� Bash, �� .

[2]
�� (read) �� , �� .

[3]
�� ? �� ($PWD), �� ? �� $PATH ��. �� - ./��_��_��.

2.2. ��

1. �� . �� .
2. �� , �� , �� , � �� . �� . (�� /�� date, who, � uptime.)