Andre Speelmans napsal(a): >> You shouldn't rely on cat or for to read a file line by line, but instead do >> this: >> >> while read line; do >> commands >> done < hosts > > I would pick this form myself, but why should one not rely on cat? It > seems to me a viable (even if useless use of cat) option. > Is there something totally wrong with relying on cat to read a file? main difference is probably in fact that commands in pipe are executed in subshell - and it means 1) some extra processes, and 2) subshell environment variables are not passed to parent shell. Thus script: #!/bin/bash echo "1: BASH_SUBSHELL=$BASH_SUBSHELL, PPID=$PPID, BASHPID=$BASHPID, \$\$=$$." N=0 cat /etc/adjtime | while read line; do ((N++)) echo " 2: BASH_SUBSHELL=$BASH_SUBSHELL, PPID=$PPID, BASHPID=$BASHPID, \$\$=$$, N=$N, line:$line." done echo "3: N=$N." will show: 1: BASH_SUBSHELL=0, PPID=5671, BASHPID=7900, $$=7900. 2: BASH_SUBSHELL=1, PPID=5671, BASHPID=7902, $$=7900, N=1, line:-0.584209 1326733538 0.000000. 2: BASH_SUBSHELL=1, PPID=5671, BASHPID=7902, $$=7900, N=2, line:1326733538. 2: BASH_SUBSHELL=1, PPID=5671, BASHPID=7902, $$=7900, N=3, line:UTC. 3: N=0. And script: #!/bin/bash echo "1: BASH_SUBSHELL=$BASH_SUBSHELL, PPID=$PPID, BASHPID=$BASHPID, \$\$=$$." N=0 while read line; do ((N++)) echo " 2: BASH_SUBSHELL=$BASH_SUBSHELL, PPID=$PPID, BASHPID=$BASHPID, \$\$=$$, N=$N, line:$line." done </etc/adjtime echo "3: N=$N." will show: 1: BASH_SUBSHELL=0, PPID=5671, BASHPID=7923, $$=7923. 2: BASH_SUBSHELL=0, PPID=5671, BASHPID=7923, $$=7923, N=1, line:-0.584209 1326733538 0.000000. 2: BASH_SUBSHELL=0, PPID=5671, BASHPID=7923, $$=7923, N=2, line:1326733538. 2: BASH_SUBSHELL=0, PPID=5671, BASHPID=7923, $$=7923, N=3, line:UTC. 3: N=3. -- users mailing list users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe or change subscription options: https://admin.fedoraproject.org/mailman/listinfo/users Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines Have a question? Ask away: http://ask.fedoraproject.org
