dash-shell

问题 I have this script, which should start a keep-alive script and Sublime Text 3 under Bash for Windows: #!/bin/dash set -e # Keep alive (in background) tail -f /dev/null & pid=$! echo "tail process id: ${pid}" echo "Keep-alive process started with Sublime Text 3\nPress SIGINT (CTRL+C) to kill it..." # Start Sublime Text 3 DISPLAY=localhost:0 /usr/bin/sublime # http://stackoverflow.com/a/19274804/1442219 trap "kill ${pid}; exit 1" INT wait This code generates: tail process id: 49 Keep-alive

问题 I'd like to list the currently defined functions in dash . Is there any way of doing that? The closest I've been able to come up with is type which can be used to test if a function exist, but other than that I'm stumped. P.S. I'm talking about dash here (not bash or zsh ). 回答1: Looking at exec.c it seems that no, there is none - the table is static, there's no such functionality in the file and none of the exported functions (unsetfunc etc) appear to offer the possibility of iterating, so

问题 I encountered a problem in my program. I have a list of files and I sort them with this code to find out the 10 most frequent file types in the list. find $DIR -type f | file -b $SAVEFILES | cut -c1-40 | sort -n | uniq -c | sort -nr | head -10 My output looks like this 168 HTML document, ASCII text 114 C source, ASCII text 102 ASCII text 33 ASCII text, with very long lines 30 HTML document, UTF-8 Unicode text, with 26 HTML document, ASCII text, with very lon 21 C source, UTF-8 Unicode text 20

问题 Say I have the path gui/site/junior/profile.py How do I get this?: gui gui/site gui/site/junior Bonus if you tell me how to loop through each path :D 回答1: You can loop with awk: awk 'BEGIN{FS=OFS="/"} { for (i=1; i<=NF; i++) { for (j=1; j<i; j++) printf "%s/", $j printf "%s\n", $i } }' <<< "gui/site/junior/profile.py" See as one liner: $ awk 'BEGIN{FS=OFS="/"}{for (i=1; i<=NF; i++) { for (j=1; j<i; j++) printf "%s%s", $j, OFS; printf "%s\n", $i}}' <<< "gui/site/junior/profile.py" gui gui/site

问题 I'm getting this error Syntax error: redirection unexpected in the line: if grep -q "^127.0.0." <<< "$RESULT" How I can run this in Ubuntu? 回答1: if grep -q "^127.0.0." <<< "$RESULT" then echo IF-THEN fi is a Bash-specific thing. If you are using a different bourne-compatable shell, try: if echo "$RESULT" | grep -q "^127.0.0." then echo IF-THEN fi 回答2: <<< is a bash-specific redirection operator (so it's not specific to Ubuntu). The documentation refers to it as a "Here String", a variant of

问题 This question already has answers here : How to escape a double quote inside double quotes? (8 answers) Closed 3 years ago . The shell command cmd may have whitespace and single and double quotes. How to escape these quotes to correctly pass the command to a POSIX shell: >dash -c ' cmd ' The other question pointed as a dup, asks about double quotes. One of the answers there is probably going to work - to split the command and use concatenated quotes. For example, if cmd were cd "dir"; ls

问题 I have bash script and it requires bash. Another person try to run it with sh script_name.sh And it fails because sh is symbolic link to dash in his distribution. $ ls -la /bin/sh lrwxrwxrwx 1 root root 4 Aug 25 16:06 /bin/sh -> dash I have an idea to use wrapper script: #!/bin/sh bash script_name.sh The goal is to run .sh script by sh with bash in system having symbolic link to dash. 回答1: Well, usually you use the shebang to tell the shell to use the correct interpreter: #!/bin/bash # your

问题 This question already has answers here : Why do shell script comparisons often use x$VAR = xyes? (7 answers) Closed last year . What is the portable and canonical way to test if variable is empty/undefined in a shell script? It should work in all sh-like shells. What I do now is something like: if [ -z "$var" ] ; then ... and for reverse, doing something when variable is not empty/undefined: if [ -n "$var" ] ; then ... And while these work for the scripts I write now, I'd like to know a way,

问题 This question already has answers here : Why do shell script comparisons often use x$VAR = xyes? (7 answers) Closed last year . What is the portable and canonical way to test if variable is empty/undefined in a shell script? It should work in all sh-like shells. What I do now is something like: if [ -z "$var" ] ; then ... and for reverse, doing something when variable is not empty/undefined: if [ -n "$var" ] ; then ... And while these work for the scripts I write now, I'd like to know a way,

问题 I am working with a Ethernet camera that comes with Busybox. A single board computer is connected to it through RS232. The SBC needs to send a single command to the camera in order to take a jpg snapshot, save it to a CF memory card and name it in a sequential order (0001, 0002 etc..). This is the code I use to take a single snapshot, without sequential naming: wget http://127.0.0.1/snap.php -O /mnt/0/snapfull`date +%d%m%y%H%M%S`.jpg I need the files to be named sequentially. This is the code