if [ -d"$DIRECTORY" ]; then # Control will enter here if $DIRECTORY exists. fi 或者检查目录是否不存在: 1 2 3 if [ ! -d"$DIRECTORY" ]; then # Control will enter here if $DIRECTORY doesn't exist. fi 但是,正如jon ericson指出的那样,如
并且注意到在插入时还可能递归(Directory::insert函数调用了Directory::insert函数)。 voidDirectory::insert(intkey,string value,boolreinserted){intbucket_no =hash(key);intstatus = buckets[bucket_no]->insert(key,value);if(status==1) {if(!reinserted) cout<<"Inserted key "<<key<<" in bucket "...
I am now going to introduce the various utility commands. Those are executed in the context of a shell, like Bash, Fish or Zsh. When you start a shell, you are going to be in your home directory. In macOS, that is found in the/Users/<yourname>/path. 我现在将介绍各种实用程序命令。
(If it does, link will return an error saying “assignment” already exists.) With links, the directory hierarchy turns from a strict hierarchy into a directed graph. (The unix file system allows links only to files, not to directories, so the graph is not only directed but acyclic. We ...
is empty" exit 0 fi # 两个变量判断是否相等 if [ "$var1" = "$var2" ]; then echo '$var1 eq $var2' else echo '$var1 not eq $var2' fi 文件的判别逻辑大全: --- -a file exists. -b file exists and is a block special file. -c file exists and is a character special file...
1) Check if the file exists: $ ls -i 1448240 a 1447274 my_ls.c 1448240 a1 1442363 output.log 1448239 "ab* 1441813 Pictures 1447139 alpha So we have a file with name “ab* in this directory 2) Try to remove it normally: $ rm "ab* ...
Full directory paths and program options may vary for different flavours of UNIX. If in doubt, consult your vendor documentation. For ease of use, the checklist has been organised into separate, logically cohesive sections. All sections are important. An abbreviated version of this checklist can...
builtin is commonly redefined this way. The return status is false if shell-builtin is not a shell builtin command. cd [-L|-P] [dir] Change the current directory to dir. The variable HOME is the default dir. The variable CDPATH defines the search path for the directory containing dir...
This also removes the example directory itself. $ rm -r example 28. cp command examples Copy file1 to file2 preserving the mode, ownership and timestamp. $ cp -p file1 file2 Copy file1 to file2. if file2 exists prompt for confirmation before overwritting it. $ cp -i file1 file2 ...
As you can see the filemath.shexists! Most of the time when you’re writing bash scripts you won’t be comparing two raw values or trying to find something out about one raw value, instead you’ll want to create a logical statement about a value contained in a variable. Variables behav...